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1.  A retrospective cohort study of leukemia and other cancers in benzene workers 
A retrospective cohort study was carried out in 1982–1983 among 28,460 benzene-exposed workers (15,643 males, 12,817 females) from 233 factories and 28,257 control workers (16,621 males, 12,366 females) from 83 factories in 12 large cities in China. All-cause mortality was significantly higher among the exposed (265.46/100,000 person-years) than among the unexposed (139.06/100,000 person-years), as was mortality from all malignant neoplasms (123.21/100,000 versus 54.7/100,000, respectively). For certain cancers, increased mortality was noted among benzene-exposed males in comparison with that among unexposed males; the standardized mortality ratios (SMR) were elevated for leukemia (SMR = 5.74), lung cancer (SMR = 2.31), primary hepatocarcinoma (SMR = 1.12), and stomach cancer (SMR = 1.22). For females only leukemia occurred in excess among the exposed. Risk of leukemia rose as duration to exposure to benzene increased up to 15 years, and then declined with additional years of exposure. Leukemia occurred among some workers with as little as 6 to 10 ppm average exposure and 50 ppm-years (or possibly less) cumulative lifetime exposure (based on all available measurements for the exposed work units). Among the 30 leukemia cases identified in the exposed cohort, the proportion of subjects with acute lymphocytic leukemia was substantially lower and the proportion with acute nonlymphocytic leukemias was higher than in the general population. During 1972 to 1981, the annual incidence of leukemia ranged from 5.83 to 28.33 per 100,000 with higher rates occurring in the interval 1977 to 1981 than in the earlier years of the study period. Future studies should evaluate more precisely the relationship between exposure levels, job title, and development of leukemia among cases and noncases within the exposed cohort.
PMCID: PMC1568128  PMID: 2792042
2.  RNA conformational requirements of self-cleavage of hepatitis delta virus RNA. 
Molecular and Cellular Biology  1990;10(10):5575-5579.
Hepatitis delta virus (HDV) RNA subfragments undergo self-cleavage at varying efficiencies. We have developed a procedure of using repeated cycles of heat denaturation and renaturation of RNA to achieve a high efficiency of cleavage. This effect can also be achieved by gradual denaturation of RNA with heat or formamide. These results suggest that only a subpopulation of the catalytic RNA molecules assumes the active conformation required for self-cleavage. This procedure could be of general use for detecting catalytic RNA activities.
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PMCID: PMC361278  PMID: 2398903
3.  Mutagenesis analysis of a hepatitis delta virus genomic ribozyme. 
Nucleic Acids Research  1993;21(18):4193-4199.
We conducted extensive mutagenesis analysis on a hepatitis delta virus (HDV) genomic ribozyme to study the sequence specificity of certain region and to derive the secondary structure associated with the catalytic core. The results confirmed that the autocatalytic domain of HDV genomic RNA contained four base-pairing regions as predicted in the 'pseudo-knot' model [Perrotta & Been (1990) Nature 350, 434-436]. The size and sequence of one of the base-pairing regions, i. e. stem-and-loop, could be flexible. Helix 3 and the first basepair of helix 1 required specific sequence to retain self-cleavage activity. The structural requirement of helix 2 was less stringent than the other base-pairing regions. Moreover, the size of helix 1 affected self-cleavage whereas the length of hinge could be variable even though the first three residues of hinge had stringent sequence requirement.
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PMCID: PMC310049  PMID: 8414973
4.  Mutagenesis analysis of the self-cleavage domain of hepatitis delta virus antigenomic RNA. 
Nucleic Acids Research  1992;20(22):5937-5941.
To determine the sequence requirements and structural features of the self-cleavage domain of hepatitis delta virus (HDV) antigenomic RNA, we constructed a series of mutants and measured the rate constant of the cleavage reaction for each. The self-cleavage activity of HDV RNA of antigenomic sense was found to reside in a region of less than 90 nucleotides in length. The catalytic domain contained a long complementary sequence which could be deleted to half of its original size. Moreover, this region could be replaced by other sequences as long as they could fold into a stem-and-loop structure. The catalytic domain also required a 6-basepair helix adjacent to the cleaving point for activity. The structural features of these two base-pairing regions are quite similar to those of the HDV genomic self-cleavage domain. The cleavage site as well as the the hinge region (the sequence between the two stems) requires specific sequences for activity.
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PMCID: PMC334457  PMID: 1461726
5.  A comparison of two phage coat protein-RNA interactions. 
Nucleic Acids Research  1988;16(11):5055-5066.
The interaction between the coat protein of the group I bacteriophage fr with its translational operator site is compared with the previously studied R17 interaction. The sequence of the two RNA binding sites differ by 2 of 20 nucleotides and two coat proteins by 17 of 129 amino acids. An analysis of the binding of fr coat protein to 24 operator variants revealed that the two proteins recognize operator sequences in virtually the same way. However, fr coat protein binds to nearly every RNA 6 to 14-fold tighter than R17 coat protein. Since the fr operator is a weaker binding variant and the fr coat protein shows a different temperature dependence of binding, it is unlikely that the two systems have different Kas in vivo. RNA fragments containing the operator sequences can initiate the capsid assembly with both fr and R17 coat protein. Surprisingly, the two coat proteins can form a mixed capsid in vitro.
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PMCID: PMC336716  PMID: 3387217

Results 1-5 (5)