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1.  A method to quantify infection and colonization of holm oak (Quercus ilex) roots by Phytophthora cinnamomi 
Plant Methods  2012;8:39.
Phytophthora cinnamomi Rands. is an important root rot pathogen widely distributed in the north hemisphere, with a large host range. Among others diseases, it is known to be a principal factor in the decline of holm oak and cork oak, the most important tree species in the “dehesa” ecosystem of south-western Spain. Previously, the focus of studies on P. cinnamomi and holm oak have been on molecular tools for identification, functional responses of the host, together with other physiological and morphological host variables. However, a microscopic index to describe the degree of infection and colonization in the plant tissues has not yet been developed. A colonization or infection index would be a useful tool for studies that examine differences between individuals subjected to different treatments or to individuals belonging to different breeding accessions, together with their specific responses to the pathogen. This work presents a methodology based on the capture and digital treatment of microscopic images, using simple and accessible software, together with a range of variables that quantify the infection and colonization process.
PMCID: PMC3495752  PMID: 22974221
Phytophthora; Holm oak decline; Microscopy; Histology; Root rot; Infection degree
2.  miR-181a Regulates Cap-Dependent Translation of p27kip1 mRNA in Myeloid Cells▿  
Molecular and Cellular Biology  2009;29(10):2841-2851.
p27kip1 (p27) is a cell cycle inhibitor and tumor suppressor whose expression is tightly regulated in the cell. Translational control of p27 mRNA has emerged as a prominent mechanism to regulate p27 expression during differentiation, quiescence, and cancer progression. The microRNAs miR-221 and miR-222 repress p27 expression in various cancer cells, and this repression promotes tumor cell proliferation. In addition, the presence of an internal ribosome entry site in the 5′ untranslated region (UTR) of p27 mRNA has been reported. Here, we show that p27 mRNA is translated via a cap-dependent mechanism in HeLa and HL60 cells and that the previously reported IRES activity can be attributed to cryptic promoters in the sequence corresponding to the p27 5′ UTR. Furthermore, cap-dependent translation of p27 mRNA is repressed by miR-181a in undifferentiated HL60 cells. Repression by miR-181a is relieved during differentiation of HL60 into monocyte-like cells, allowing the accumulation of p27, which is necessary to fully block cell cycle progression and reach terminal differentiation. These results identify miR-181a as a regulator of p27 mRNA translation during myeloid cell differentiation.
PMCID: PMC2682024  PMID: 19273599
3.  Regulation of Translation by Ribosome Shunting through Phosphotyrosine-Dependent Coupling of Adenovirus Protein 100k to Viral mRNAs  
Journal of Virology  2005;79(9):5676-5683.
Adenovirus simultaneously inhibits cap-dependent host cell mRNA translation while promoting the translation of its late viral mRNAs during infection. Studies previously demonstrated that tyrosine kinase activity plays a central role in the control of late adenovirus protein synthesis. The tyrosine kinase inhibitor genistein decreases late viral mRNA translation and prevents viral inhibition of cellular protein synthesis. Adenovirus protein 100k blocks cellular mRNA translation by disrupting the cap-initiation complex and promotes viral mRNA translation through an alternate mechanism known as ribosome shunting. 100k protein interaction with initiation factor eIF4G and the viral 5′ noncoding region on viral late mRNAs, known as the tripartite leader, are both essential for ribosome shunting. We show that adenovirus protein 100k promotes ribosome shunting in a tyrosine phosphorylation-dependent manner. The primary sites of phosphorylated tyrosine on protein 100k were mapped and mutated, and two key sites are shown to be essential for protein 100k to promote ribosome shunting. Mutation of the two tyrosine phosphorylation sites in 100k protein does not impair interaction with initiation factor 4G, but it severely reduces association of 100k with tripartite leader mRNAs. 100k protein therefore promotes ribosome shunting and selective translation of viral mRNAs by binding specifically to the adenovirus tripartite leader in a phosphotyrosine-dependent manner.
PMCID: PMC1082770  PMID: 15827182
4.  Structural Basis for Competitive Inhibition of eIF4G-Mnk1 Interaction by the Adenovirus 100-Kilodalton Protein 
Journal of Virology  2004;78(14):7707-7716.
Translation of most cellular mRNAs involves cap binding by the translation initiation complex. Among this complex of proteins are cap-binding protein eIF4E and the eIF4E kinase Mnk1. Cap-dependent mRNA translation generally correlates with Mnk1 phosphorylation of eIF4E when both are bound to eIF4G. During the late phase of adenovirus (Ad) infection translation of cellular mRNA is inhibited, which correlates with displacement of Mnk1 from eIF4G by the viral 100-kDa (100K) protein and dephosphorylation of eIF4E. Here we describe the molecular mechanism for 100K protein displacement of Mnk1 from eIF4G and elucidate a structural basis for eIF4G interaction with Mnk1 and 100K proteins and Ad inhibition of cellular protein synthesis. The eIF4G-binding site is located in an N-terminal 66-amino-acid peptide of 100K which is sufficient to bind eIF4G, displace Mnk1, block eIF4E phosphorylation, and inhibit eIF4F (cap)-dependent cellular mRNA translation. Ad 100K and Mnk1 proteins possess a common eIF4G-binding motif, but 100K protein binds more strongly to eIF4G than does Mnk1. Unlike Mnk1, for which binding to eIF4G is RNA dependent, competitive binding by 100K protein is RNA independent. These data support a model whereby 100K protein blocks cellular protein synthesis by coopting eIF4G and cap-initiation complexes regardless of their association with mRNA and displacing or blocking binding by Mnk1, which occurs only on preassembled complexes, resulting in dephosphorylation of eIF4E.
PMCID: PMC434077  PMID: 15220445
5.  GCD14p, a Repressor of GCN4 Translation, Cooperates with Gcd10p and Lhp1p in the Maturation of Initiator Methionyl-tRNA in Saccharomyces cerevisiae† 
Molecular and Cellular Biology  1999;19(6):4167-4181.
Gcd10p and Gcd14p were first identified genetically as repressors of GCN4 mRNA translation in Saccharomyces cerevisiae. Recent findings indicate that Gcd10p and Gcd14p reside in a nuclear complex required for the presence of 1-methyladenosine in tRNAs. Here we show that Gcd14p is an essential protein with predicted binding motifs for S-adenosylmethionine, consistent with a direct function in tRNA methylation. Two different gcd14 mutants exhibit defects in cell growth and accumulate high levels of initiator methionyl-tRNA (tRNAiMet) precursors containing 5′ and 3′ extensions, suggesting a defect in processing of the primary transcript. Dosage suppressors of gcd10 mutations, encoding tRNAiMet (hcIMT1 to hcIMT4; hc indicates that the gene is carried on a high-copy-number plasmid) or a homologue of human La protein implicated in tRNA 3′-end formation (hcLHP1), also suppressed gcd14 mutations. In fact, the lethality of a GCD14 deletion was suppressed by hcIMT4, indicating that the essential function of Gcd14p is required for biogenesis of tRNAiMet. A mutation in GCD10 or deletion of LHP1 exacerbated the defects in cell growth and expression of mature tRNAiMet in gcd14 mutants, consistent with functional interactions between Gcd14p, Gcd10p, and Lhp1p in vivo. Surprisingly, the amounts of NME1 and RPR1, the RNA components of RNases P and MRP, were substantially lower in gcd14 lhp1::LEU2 double mutants than in the corresponding single mutants, whereas 5S rRNA was present at wild-type levels. Our findings suggest that Gcd14p and Lhp1p cooperate in the maturation of a subset of RNA polymerase III transcripts.
PMCID: PMC104376  PMID: 10330157

Results 1-5 (5)