Search tips
Search criteria

Results 1-25 (39)

Clipboard (0)
more »
Year of Publication
Document Types
1.  Short Intussusception Valves Prevent Reflux After Jejunal Interposition Bilioduodenal Anastomosis 
HPB Surgery  1991;5(1):29-34.
Short whole circumference and semi-circumference intussusception valves were created in interposition cholecysto-jejunal-duodenal conduits in pigs to determine which method best prevented gastrointestinal reflux into the biliary tract. Following intravenous injection of 99 mTc-HIDA the time interval for its excretion from the liver and appearance in the duodenum was not different in either whole or semi-circumference valve animals or in controls without valves. After intragastric administration of 99 mTc-DTPA the relative radioactivity of gallbladder contents (reflux) in the cohort without valves was significantly higher than in both cohorts with valves. Animals with semi-circumferential valves in turn had significantly higher levels of nuclide than those with whole circumference valves. Reflux was observed grossly in 100% of animals without valves, in 20% of those with semi-circumference valves, and in no animals with whole circumference valves. This study indicates that both Whole and semi-circumference intussusception valves placed in jejunal biliary conduits allow unimpeded flow of bile into the gastrointestinal tract. Whole circumference valves are more effective for prevention of reflux than semi-circumferential valves.
PMCID: PMC2442931  PMID: 1777408
3.  HTLV-1 associated T cell lymphoma in South East Asia: case report and family study. 
Journal of Clinical Pathology  1991;44(8):692-693.
Geographic clustering of human T cell lymphoma/leukaemia virus type 1 (HTLV-1) infection is well recognised, particularly in south western Japan, parts of West and Central Africa, the south eastern United States and the Caribbean islands. Sporadic cases have been reported in many other parts of the world. The first case of HTLV-1 associated leukaemia/lymphoma (ATLL) in South East Asia is reported. Contact tracing showed a high incidence of carriers among the relatives.
PMCID: PMC496769  PMID: 1890205
4.  Preparation, characterization, and immunogenicity of conjugates composed of the O-specific polysaccharide of Shigella dysenteriae type 1 (Shiga's bacillus) bound to tetanus toxoid. 
Infection and Immunity  1991;59(12):4450-4458.
The background for developing conjugate vaccines for shigellosis composed of the O-specific polysaccharide (O-SP) bound to a protein is described elsewhere (C. Y. Chu, R. Schneerson, and J. B. Robbins, submitted for publication). Briefly, there is direct evidence for type (lipopolysaccharide [LPS])-specific protection after infection with the wild type or with attenuated strains of shigellae. Prospective studies of Israeli armed forces recruits show a correlation between preexisting serum immunoglobulin G (IgG) LPS antibodies and resistance to shigellosis (D. Cohen, M. S. Green, C. Block, R. Slephon, and I. Ofek, J. Clin. Microbiol. 29:386-389, 1991). In order to elicit IgG LPS-specific antibodies to Shigella dysenteriae type 1, the O-SP of this pathogen was purified and bound to tetanus toxoid (TT) by three schemes. The most immunogenic used a modification of a published method (C. Y. Chu, R. Schneerson, J. B. Robbins, and S. C. Rastogi, Infect. Immun. 40:245-256, 1983). The resultant O-SP-TT conjugates were stable and elicited high levels of IgG O-SP antibodies and booster responses in young mice when injected subcutaneously in saline at 1/10 the proposed human dose. Adsorption onto alum or concurrent administration with monophosphoryl lipid A enhanced both the IgG and IgM antibody responses to the O-SP of the conjugate; both the nonadsorbed and adsorbed conjugates elicited higher rises of IgG than of IgM antibodies. Clinical evaluations of S. dysenteriae type 1 O-SP-TT conjugates are planned.
PMCID: PMC259062  PMID: 1937803
5.  Structural analysis and transcriptional mapping of the Marek's disease virus gene encoding pp38, an antigen associated with transformed cells. 
Journal of Virology  1991;65(12):6509-6515.
The gene encoding a Marek's disease virus (MDV) pp38 phosphoprotein has been identified, sequenced, and localized to the BamHI H fragment to the left of the putative MDV origin of replication. The open reading frame was defined by sequencing of a lacZ-pp38 fusion protein gene from a lambda gt11 expression library. The entire open reading frame is 290 amino acids long and codes for a protein with a calculated molecular weight of 31,169, compared with the size of 38 kDa of the phosphorylated form estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. S1 nuclease protection analysis showed that the pp38 gene is transcribed leftward as an unspliced mRNA. On the basis of transcriptional mapping studies, the pp38 transcript is predicted to be about 1.8 kb in length without a poly(A) sequence. Its promoter-enhancer region overlaps that of the major rightward BamHI H 1.8-kb transcript implicated in tumor induction. This region contains Oct-1, Sp1, and CCAAT motifs as well as the putative origin of replication. The pp38 protein is the only presently known antigen that is consistently associated with the transformation state. It may play a significant role in MDV transformation.
PMCID: PMC250698  PMID: 1658357
6.  Comparison of conventional susceptibility tests with direct detection of penicillin-binding protein 2a in borderline oxacillin-resistant strains of Staphylococcus aureus. 
Antimicrobial Agents and Chemotherapy  1991;35(12):2574-2579.
Six selected strains of Staphylococcus aureus classified as borderline oxacillin-resistant, according to standard disk diffusion and microdilution susceptibility test methods, and seven methicillin-resistant and seven methicillin-susceptible control strains were examined for the presence of penicillin-binding protein 2a (PBP 2a) by fluorography and immunoblotting and for DNA hybridization with a mec-specific probe in a dot blot assay. Oxacillin agar screen tests with and without NaCl supplementation were also performed with all strains. PBP 2a was detected both by fluorography and by immunoblotting in all seven methicillin-resistant control strains and in none of the susceptible controls. PBP 2a was detected in two borderline strains. Results of agar screen tests performed without NaCl supplementation were completely concordant with susceptibility determined by PBP 2a and mec detection methods. Agar screening with NaCl supplementation was less accurate. These findings were confirmed with 20 additional borderline strains. Direct detection methods for the presence of PBP 2a or mec, the gene encoding it, allow accurate and definitive classification of borderline strains. Further efforts to develop a rapid, clinically useful, antibody detection system for PBP 2a are warranted.
PMCID: PMC245433  PMID: 1810191
7.  A comparative study of the promotion of tissue plasminogen activator and pro-urokinase-induced plasminogen activation by fragments D and E-2 of fibrin. 
Journal of Clinical Investigation  1991;88(6):2012-2017.
Plasmin generation by equimolar concentrations of tissue plasminogen activator (t-PA), pro-urokinase (pro-UK), and urokinase (UK), and a twofold higher concentration of a plasmin-resistant mutant rpro-UK (Ala-158-pro-UK) was measured on a microtiter plate reader. The promoting effects on this reaction of equimolar concentrations of fibrinogen, soluble fibrin (Desafib), CNBr fragment FCB-2 (an analogue of fragment D), or purified fragment E-2 were compared. Plasmin generation by t-PA was moderately promoted by fibrinogen, substantially promoted by Desafib and FCB-2, but not at all promoted by fragment E-2. By contrast, plasmin generation by pro-UK or by Ala-158-pro-UK was not promoted either by fibrinogen, Desafib, or FCB-2, but was significantly promoted by fragment E-2. Plasmin generation by UK was not significantly promoted by any of the fibrin(ogen) preparations. Treatment of fragment E-2 by carboxypeptidase-B (CPB), eliminated its promotion of pro-UK and Ala-158-pro-UK-induced plasmin generation. Pretreatment of FCB-2 with plasmin slightly potentiated its promotion of t-PA activity. This effect of plasmin pretreatment of FCB-2 was reversed by CPB treatment. Plasmin pretreatment of FCB-2 did not induce any promotion of activity in pro-UK or Ala-158-pro-UK. The findings show that the intrinsic activity of pro-UK and the activity of t-PA are promoted by different regions of the fibrin(ogen) molecule. The latter is stimulated primarily by a determinant in the fragment D region, which is available in intact fibrin. By contrast, plasminogen activation by the intrinsic activity of pro-UK was stimulated exclusively by fragment E-2, which is unavailable in intact fibrin. The findings are believed relevant to fibrinolysis and support the concept that t-PA and pro-UK are complementary, sequential, and synergistic in their actions.
PMCID: PMC295789  PMID: 1836471
8.  Effects of lysophosphatidylcholine on electrophysiological properties and excitation-contraction coupling in isolated guinea pig ventricular myocytes. 
Journal of Clinical Investigation  1991;88(6):1819-1832.
Lysophosphoglyceride accumulation in ischemic myocardium has been implicated as a cause of arrhythmias. We examined the effects of lysophosphatidylcholine (LPC) in isolated guinea pig ventricular myocytes. In paced myocytes loaded with the Ca2+ indicator Indo-1-AM and studied at room temperature, 20 microM LPC caused an initial positive inotropic effect followed by spontaneous automaticity, a decline in active cell shortening, and progressive diastolic shortening (contracture) leading to cell death. These changes were accompanied by a progressive increase in cytosolic [Ca2+]i. In patch-clamped myocytes dialyzed internally with high EGTA concentrations, LPC caused membrane depolarization, shortening of the action potential duration, and abnormal automaticity as seen in multicellular preparations. Voltage clamp experiments revealed the appearance of a nonselective leak conductance without significant changes in the delayed rectifier K+ current, inward rectifier K+ current, L-type Ca2+ current, and T-type Ca2+ current. Pretreatment with 20 mM caffeine and [Ca2+]o-free solution did not prevent the leak current. In patch clamped myocytes loaded with 0.1 mM Fura-2 salt, the [Ca2+]i transient induced by either voltage clamps or brief caffeine exposure remained normal until the nonselective leak current developed. The Na(+)-Ca2+ exchange current elicited during caffeine-induced [Ca2+]i transients also did not appear to be altered by LPC. Qualitatively similar results were obtained in myocytes studied at 35 degrees C. The membrane detergent saponin (0.005% wt/wt) mimicked all of the effects of LPC. We conclude that under these experimental conditions the effects of LPC are most compatible with a detergent action causing membrane leakiness with resultant depolarization, [Ca2+]i overload, and contracture.
PMCID: PMC295749  PMID: 1721623
9.  Lipoxygenase metabolites of arachidonic and linoleic acids modulate the adhesion of tumor cells to endothelium via regulation of protein kinase C. 
Cell Regulation  1991;2(12):1045-1055.
12(S)-hydroxyeicosatetraenoic acid (12[S]-HETE) and 13(S)-hydroxyoctadecadienoic acid (13[S]-HODE), lipoxygenase metabolites of arachidonic acid and linoleic acid, respectively, previously have been suggested to regulate tumor cell adhesion to endothelium during metastasis. Adhesion of rat Walker carcinosarcoma (W256) cells to a rat endothelial cell monolayer was enhanced after treatment with 12(S)-HETE and this 12(S)-HETE enhanced adhesion was blocked by 13(S)-HODE. Protein kinase inhibitors, staurosporine, calphostin C, and 1-(5-isoquinoline-sulfonyl)-2-methylpiperazine, inhibited the 12(S)-HETE enhanced W256 cell adhesion. Depleting W256 cells of protein kinase C (PKC) with phorbol 12-myristate-13-acetate abolished their ability to respond to 12(S)-HETE. Treatment of W256 cells with 12(S)-HETE induced a 100% increase in membrane-associated PKC activity whereas 13(S)-HODE inhibited the effect of 12(S)-HETE on PKC translocation. High-performance liquid chromatographic analysis revealed that in W256 cells 12-HETE and 13-HODE were two of the major lipoxygenase metabilites of arachidonic acid and linoleic acid, respectively. Therefore, these two metabolites may provide an alternative signaling pathway for the regulation of PKC. Further, these findings suggest that the regulation of tumor cell adhesion to endothelium by 12(S)-HETE and 13(S)-HODE may be a PKC-dependent process.
PMCID: PMC361904  PMID: 1801923
10.  Chorionic villus sampling 
BMJ : British Medical Journal  1991;303(6814):1402.
PMCID: PMC1671590
11.  Specific binding of host cell proteins to the 3'-terminal stem-loop structure of rubella virus negative-strand RNA. 
Journal of Virology  1991;65(11):5961-5967.
At the 5' end of the rubella virus genomic RNA, there are sequences that can form a potentially stable stem-loop (SL) structure. The complementary negative-strand equivalent of the 5'-end SL structure of positive-strand rubella virus RNA [5' (+) SL structure] is thought to serve as a promoter for the initiation of positive-strand synthesis. We screened the negative-strand equivalent of the 5' (+) SL structure (64 nucleotides) and the adjacent region of the negative-strand RNA for their ability to bind to host cell proteins. Specific binding to the 64-nucleotide-long potential SL structure of three cytosolic proteins with relative molecular masses of 97, 79, and 56 kDa was observed by UV-induced covalent cross-linking. There was a significant increase in the binding of the 97-kDa protein from cells upon infection with rubella virus. Altering the SL structure by deleting sequences in either one of the two potential loops abolished the binding interaction. The 56-kDa protein also appeared to bind specifically to an SL derived from the 3' end of positive-strand RNA. The 3'-terminal structure of rubella virus negative-strand RNA shared the same protein-binding activity with similar structures in alphaviruses, such as Sindbis virus and eastern equine encephalitis virus. A possible role for the host proteins in the replication of rubella virus and alphaviruses is discussed.
PMCID: PMC250260  PMID: 1920622
12.  Conversion of Bacillus subtilis 168 to a subtilin producer by competence transformation. 
Journal of Bacteriology  1991;173(22):7387-7390.
Subtilin is a ribosomally synthesized peptide antibiotic produced by Bacillus subtilis ATCC 6633. B. subtilis 168 was converted to a subtilin producer by competence transformation with chromosomal DNA from B. subtilis ATCC 6633. A chloramphenicol acetyltransferase gene was inserted next to the subtilin structural gene as a selectable marker. The genes that conferred subtilin production were derived from a 40-kb region of the B. subtilis ATCC 6633 chromosome that had flanking homologies to the B. subtilis 168 chromosome. The subtilin produced by the mutant was identical to natural subtilin in its biological activity, chromatographic behavior, amino acid composition, and N-terminal amino acid sequence.
PMCID: PMC209249  PMID: 1938928
13.  Site-specific mutagenesis method which completely excludes wild-type DNA from the transformants. 
Lee, N | Liu, J | He, C | Testa, D
Applied and Environmental Microbiology  1991;57(10):2888-2890.
A highly efficient site-specific mutagenesis method has been devised to exclude wild-type DNA from incorporation into the transformed cells. Two complementary oligonucleotides, corresponding to a target sequence of a DNA molecule and containing an insertion mutation which created an endonuclease restriction site, were synthesized. By using the wild-type DNA molecule flanked by two restriction sites on each side of the target region as a template, the two oligonucleotide primers were extended, enriched, and isolated. The extended products, in turn, were used as templates in a polymerase chain reaction to obtain a mutagenized double-stranded DNA fragment which was conveniently cloned into plasmids by using the flanking restriction sites. Escherichia coli cells transformed by these plasmids were subject to large-scale analysis. One hundred percent of the transformants examined by colony hybridization, restriction enzyme analysis, and DNA sequencing were found to contain the mutant DNA sequence.
PMCID: PMC183891  PMID: 1746949
14.  The herpes simplex virus 1 gene encoding a protease also contains within its coding domain the gene encoding the more abundant substrate. 
Journal of Virology  1991;65(10):5149-5156.
The herpes simplex virus 1 open reading frames UL26 and UL26.5 are 3' coterminal. The larger, UL26 open reading frame encodes a protein approximately 80,000 in apparent molecular weight and contains the promoter and coding sequence of the UL26.5 gene, which specifies a capsid protein designated infected cell protein 35. The larger product contains in its entirety the amino acid sequence of the smaller protein. We report that the UL26 gene encodes a protease which catalyzes its own cleavage and that of the more abundant product of UL26.5. By inserting the coding sequence of an epitope to a cytomegalovirus monoclonal antibody and homologs of the immunoglobulin G binding domain of staphylococcal protein A into the 3' termini of the coding domains of the two open reading frames, we identified both products of the cleavage and determined that the cleavage site is approximately 20 amino acids from the carboxyl termini of both proteins.
PMCID: PMC248991  PMID: 1654435
15.  axl, a transforming gene isolated from primary human myeloid leukemia cells, encodes a novel receptor tyrosine kinase. 
Molecular and Cellular Biology  1991;11(10):5016-5031.
Using a sensitive transfection-tumorigenicity assay, we have isolated a novel transforming gene from the DNA of two patients with chronic myelogenous leukemia. Sequence analysis indicates that the product of this gene, axl, is a receptor tyrosine kinase. Overexpression of axl cDNA in NIH 3T3 cells induces neoplastic transformation with the concomitant appearance of a 140-kDa axl tyrosine-phosphorylated protein. Expression of axl cDNA in the baculovirus system results in the expression of the appropriate recombinant protein that is recognized by antiphosphotyrosine antibodies, confirming that the axl protein is a tyrosine kinase. The juxtaposition of fibronectin type III and immunoglobulinlike repeats in the extracellular domain, as well as distinct amino acid sequences in the kinase domain, indicate that the axl protein represents a novel subclass of receptor tyrosine kinases.
PMCID: PMC361494  PMID: 1656220
16.  An epidemiological study of lung cancer in Xuan Wei County, China: current progress. Case-control study on lung cancer and cooking fuel. 
In Xuan Wei County, Yunnan Province, lung cancer mortality rates are among China's highest in males and females. Previous studies have shown a strong association of lung cancer mortality with air pollution from "smoky" coal combustion. In the present quantitative risk assessment of indoor air pollution study, the result strongly shows an obvious on-site exposure-response relationship between benzo[a]pyrene concentration in indoor air and lung cancer mortality and strongly supports the hypothesis that indoor air pollution is the main risk factor in inducing lung cancer in Xuan Wei County. In the present case-control study, the result shows that in females, the presence of lung cancer is statistically significantly associated with chronic bronchitis and family history of lung cancer. The results also suggest an association of lung cancer with duration of cooking food, but not with passive smoking. In males, the presence of lung cancer is associated with smoking, bronchitis, family history of lung cancer, and personal history of cooking food.
PMCID: PMC1567943  PMID: 1954946
17.  Irritant effects of formaldehyde exposure in mobile homes. 
This paper reports the irritant effects associated with formaldehyde exposures in mobile homes. Week-long, integrated formaldehyde concentrations were measured using passive monitors in summer and winter while the mobile home residents continued their normal activities. Information on acute health problems, chronic respiratory/allergic illnesses, smoking behavior, demographic variables, and time spent at home was obtained on over 1000 individuals during the sampling period. Measured formaldehyde concentrations varied from under the limit of detection (0.01 ppm) to 0.46 ppm. Formaldehyde exposure was estimated for each individual by multiplying the concentration measured in his or her home by the time he or she spent at home. Irritant effects were found to be associated with formaldehyde exposure after controlling for age, sex, smoking status, and chronic illnesses using a logistic procedure. Some of the interaction terms found to be significant indicated that there were synergistic effects between formaldehyde exposure and chronic health problems.
PMCID: PMC1567965  PMID: 1954947
18.  Relationships among the rfb regions of Salmonella serovars A, B, and D. 
Journal of Bacteriology  1991;173(15):4814-4819.
The O antigens of Salmonella serogroups A, B, and D differ structurally in their side chain sugar residues. The genes encoding O-antigen biosynthesis are clustered in the rfb operon. The gene rfbJ in strain LT2 (serovar typhimurium, group B) and the genes rfbS and rfbE in strain Ty2 (serovar typhi, group D) account for the known differences in the rfb gene clusters used for determination of group specificity. In this paper, we report the nucleotide sequence of 2.9 kb of DNA from the rfb gene cluster of strain Ty2 and the finding of two open reading frames which have limited similarity with the corresponding open reading frames of strain LT2. These two genes complete the sequence of the rfb region of group D strain Ty2 if we use strain LT2 sequence where restriction site data show it to be extremely similar to the strain Ty2 sequence. The restriction map of the rfb gene cluster in group A strain IMVS1316 (serovar paratyphi) is identical to that of the cluster in strain Ty2 except for a frameshift mutation in rfbE and a triplicated region. The rfb gene clusters of these three strains are compared, and the evolutionary origin of these genes is discussed.
PMCID: PMC208160  PMID: 1856174
19.  Genetic evidence for interaction between the CheW and Tsr proteins during chemoreceptor signaling by Escherichia coli. 
Journal of Bacteriology  1991;173(16):4941-4951.
This study presents two lines of genetic evidence consistent with the premise that CheW, a cytoplasmic component of the chemotactic signaling system of Escherichia coli, interacts directly with Tsr, the membrane-bound serine chemoreceptor. (i) We demonstrated phenotypic suppression between 10 missense mutant CheW proteins and six missense mutant Tsr proteins. Most of these mutant proteins had leaky chemotaxis defects and were partially dominant, implying relatively minor functional alterations. Their suppression pattern was allele specific, suggesting that the mutant proteins have compensatory conformational changes at sites of interactive contact. (ii) We isolated five partially dominant CheW mutations and found that four of them were similar or identical to the suppressible CheW mutant proteins. This implies that there are only a few ways in which CheW function can be altered to produce dominant defects and that dominance is mediated through interactions of CheW with Tsr. The amino acid replacements in these mutant proteins were inferred from their DNA sequence changes. The CheW mutations were located in five regularly spaced clusters in the first two-thirds of the protein. The Tsr mutations were located in a highly conserved region in the middle of the cytoplasmic signaling domain. The hydrophobic moments, overall hydrophobicities, and predicted secondary structures of the mutant segments were consistent with the possibility that they are located at the surface of the CheW and Tsr molecules and represent the contact sites between these two proteins.
PMCID: PMC208182  PMID: 1860813
20.  A functional leuABCD operon is required for leucine synthesis by the tyrosine-repressible transaminase in Escherichia coli K-12. 
Journal of Bacteriology  1991;173(12):3864-3871.
In Escherichia coli K-12, two enzymes, encoded by ilvE and tyrB, catalyze the amination of 2-ketoisocaproate (2-KIC) to form leucine. Although leucine-requiring derivatives of an ilvE strain that are unable to grow on 2-KIC were expected to have mutations only in tyrB, mapping studies showed that one such mutation was tightly linked to the leu operon (at 1.5 min), not to tyrB (at 92 min). Chromosomal fragments cloned because they complemented this mutation were found to complement leu mutations, and vice versa, but none of these fragments complemented a tyrB mutation. The Tn5 insertion and flanking host DNA from this anomalous mutant was cloned in vivo, using Mu dII4042, and an in vivo procedure was developed to isolate deletion derivatives of Tn5-containing plasmids. These deletion plasmids were used to determine the DNA sequences flanking the transposon. The data showed that Tn5 was inserted between bp 122 and 132 in the leu leader. In addition, other ilvE leu double mutants were found to be unable to grow on 2-KIC in place of leucine. The accumulation of 2-ketoisovalerate in ilvE leu double mutants was shown to interfere with 2-KIC amination by the tyrB-encoded transaminase and also by the aspC- and avtA-encoded transaminases (which are able to catalyze this reaction in vivo when the corresponding genes are present on multicopy plasmids).
PMCID: PMC208018  PMID: 1646790
21.  Degradation of the Herbicide Glyphosate by Members of the Family Rhizobiaceae 
Several strains of the family Rhizobiaceae were tested for their ability to degrade the phosphonate herbicide glyphosate (isopropylamine salt of N-phosphonomethylglycine). All organisms tested (seven Rhizobium meliloti strains, Rhizobium leguminosarum, Rhizobium galega, Rhizobium trifolii, Agrobacterium rhizogenes, and Agrobacterium tumefaciens) were able to grow on glyphosate as the sole source of phosphorus in the presence of the aromatic amino acids, although growth on glyphosate was not as fast as on Pi. These results suggest that glyphosate degradation ability is widespread in the family Rhizobiaceae. Uptake and metabolism of glyphosate were studied by using R. meliloti 1021. Sarcosine was found to be the immediate breakdown product, indicating that the initial cleavage of glyphosate was at the C—P bond. Therefore, glyphosate breakdown in R. meliloti 1021 is achieved by a C—P lyase activity.
PMCID: PMC183471  PMID: 16348512
22.  Phylogenetic analysis and evolution of RNase P RNA in proteobacteria. 
Journal of Bacteriology  1991;173(12):3855-3863.
The secondary structures of the eubacterial RNase P RNAs are being elucidated by a phylogenetic comparative approach. Sequences of genes encoding RNase P RNA from each of the recognized subgroups (alpha, beta, gamma, and delta) of the proteobacteria have now been determined. These sequences allow the refinement, to nearly the base pair level, of the phylogenetic model for RNase P RNA secondary structure. Evolutionary change among the RNase P RNAs was found to occur primarily in four discrete structural domains that are peripheral to a highly conserved core structure. The new sequences were used to examine critically the proposed similarity (C. Guerrier-Takada, N. Lumelsky, and S. Altman, Science 246:1578-1584, 1989) between a portion of RNase P RNA and the "exit site" of the 23S rRNA of Escherichia coli. Phylogenetic comparisons indicate that these sequences are not homologous and that any similarity in the structures is, at best, tenuous.
PMCID: PMC208017  PMID: 1711030
23.  Strand breaks without DNA rearrangement in V (D)J recombination. 
Molecular and Cellular Biology  1991;11(6):3155-3162.
Somatic gene rearrangement of immunoglobulin and T-cell receptor genes [V(D)J recombination] is mediated by pairs of specific DNA sequence motifs termed signal sequences. In experiments described here, retroviral vectors containing V(D)J rearrangement cassettes in which the signal sequences had been altered were introduced into wild-type and scid (severe combined immune deficiency) pre-B cells and used to define intermediates in the V(D)J recombination pathway. The scid mutation has previously been shown to deleteriously affect the V(D)J recombination process. Cassettes containing a point mutation in one of the two signal sequences inhibited rearrangement in wild-type cells. In contrast, scid cells continued to rearrange these cassettes with the characteristic scid deletional phenotype. Using these mutated templates, we identified junctional modifications at the wild-type signal sequences that had arisen from strand breaks which were not associated with overall V(D)J rearrangements. Neither cell type was able to rearrange constructs which contained only a single, nonmutated, signal sequence. In addition, scid and wild-type cell lines harboring cassettes with mutations in both signal sequences did not undergo rearrangement, suggesting that at least one functional signal sequence was required for all types of V(D)J recombination events. Analysis of these signal sequence mutations has provided insights into intermediates in the V(D)J rearrangement pathway in wild-type and scid pre-B cells.
PMCID: PMC360165  PMID: 2038323
24.  The epidermal growth factor receptor phosphorylates GTPase-activating protein (GAP) at Tyr-460, adjacent to the GAP SH2 domains. 
Molecular and Cellular Biology  1991;11(5):2511-2516.
GTPase-activating protein (GAP) stimulates the ability of p21ras to hydrolyze GTP to GDP. Since GAP is phosphorylated by a variety of activated or oncogenic protein-tyrosine kinases, it may couple tyrosine kinases to the Ras signaling pathway. The epidermal growth factor (EGF) receptor cytoplasmic domain phosphorylated human GAP in vitro within a single tryptic phosphopeptide. The same GAP peptide was also apparently phosphorylated on tyrosine in EGF-stimulated rat fibroblasts. Circumstantial evidence suggested that residue 460 might be the site of GAP tyrosine phosphorylation. This possibility was confirmed by phosphorylation of a synthetic peptide corresponding to the predicted tryptic peptide containing Tyr-460. Alteration of Tyr-460 to phenylalanine by site-directed mutagenesis diminished the in vitro phosphorylation of a bacterial GAP polypeptide by the EGF receptor. We conclude that Tyr-460 is a site of GAP tyrosine phosphorylation by the EGF receptor in vitro and likely in vivo. GAP Tyr-460 is located immediately C terminal to the second GAP SH2 domain, suggesting that its phosphorylation might have a role in regulating protein-protein interactions.
PMCID: PMC360020  PMID: 1850098
25.  Interaction of a lens cell transcription factor with the proximal domain of the mouse gamma F-crystallin promoter. 
Molecular and Cellular Biology  1991;11(3):1531-1537.
The elements regulating lens-specific expression of the mouse gamma F-crystallin gene were examined. Here we show that mouse gamma F-crystallin sequences -67 to +45 contain a low basal level of lens-specific promoter activity and that sequences -67 to -25, which are highly conserved among different gamma-crystallin genes, are able to function as a strong transcriptional activator when duplicated and placed upstream of the TATA box. We also show that nuclear factors from lens and nonlens cells are able to form different complexes with sequences centered at -46 to -36 and demonstrate that binding of the factor from lens cells correlates with lens-specific promoter activity of the mouse gamma F-crystallin gene.
PMCID: PMC369438  PMID: 1996107

Results 1-25 (39)