RESUMEN
Two highly conserved RuvB-like putative DNA helicases, p47/TIP49b and p50/TIP49a, have been identified in the eukaryotes. Here, we study the function of Saccharomyces cerevisiae TIH2, which corresponds to mammalian p47/TIP49b. Tih2p is required for vegetative cell growth and localizes in the nucleus. Immunoprecipitation analysis revealed that Tih2p tightly interacts with Tih1p, the counterpart of mammalian p50/TIP49a, which has been shown to interact with the TATA-binding protein and the RNA polymerase II holoenzyme complex. Furthermore, the mutational study of the Walker A motif, which is required for nucleotide binding and hydrolysis, showed that this motif plays indispensable roles in the function of Tih2p. When a temperature-sensitive tih2 mutant, tih2-160, was incubated at the nonpermissive temperature, cells were rapidly arrested in the G(1) phase. Northern blot analysis revealed that Tih2p is required for transcription of G(1) cyclin and of several ribosomal protein genes. The similarities between the mutant phenotypes of tih2-160 and those of taf145 mutants suggest a role for TIH2 in the regulation of RNA polymerase II-directed transcription.
Asunto(s)
Proteínas Portadoras/genética , Ciclo Celular/genética , ADN Helicasas , Proteínas Fúngicas/genética , ARN Polimerasa II/genética , Saccharomyces cerevisiae/genética , Proteínas Bacterianas/genética , Proteínas Portadoras/biosíntesis , Proteínas Fúngicas/biosíntesis , Regulación Fúngica de la Expresión Génica , Saccharomyces cerevisiae/citología , Transcripción GenéticaRESUMEN
Tubal metaplasia (TM) of the uterine cervix may be confused with endocervical glandular dysplasia or adenocarcinoma of the uterine cervix in histologic specimens. TM is characterized histologically by architecturally normal endocervical glands containing ciliated or clear cells, nonciliated cells, and intercalated or peg cells, resembling normal tubal mucosa. Although several characteristics of TM are still undetermined, TM is considered a benign lesion. In this study, the expressions of epithelial-specific antigen (ESA), epidermal growth factor receptor (EGFR), and fucosyl SSEA1 (Le(y)) antigens were examined by an immunohistochemical method in 14 cases of TM in the uterine cervix (5 with normal endocervix, 5 with endocervical glandular dysplasia, 3 with adenocarcinoma in situ, and 1 with microinvasive adenocarcinoma). In the normal endocervical cells, expression of the EGFR antigen was rarely observed in the cytoplasm, and ESA staining was generally restricted to the basolateral membrane. Le(y) expression was occasionally observed in the cytoplasm of subcolumnar reserve cells. On the other hand, expression of EGFR, ESA, and Le(y) was observed in the cytoplasm of TM as well as in adenocarcinomas of the uterine cervix. These results suggest that TM in the uterine cervix might possess a neoplastic character.
