| Summary: | 博士 === 國立陽明大學 === 生化暨分子生物研究所 === 94 === The telomeres of Saccharomyces cerevisiae are composed of ~250-300 bp double-stranded (TG1-3)n/(C1-3A)n and a single-stranded TG1-3 tail. They maintain chromosome integrity and stability. Gbp2p is identified as a single-strand TG1-3 DNA binding protein in vitro. It affects telomere localization since the localization of Rap1p in nuclei was altered in cells deleted of GBP2. Gbp2p overexpression restores the growth arrest and telomere length phenotype in cdc13-1, a temperature-sensitive mutant of an essential telomere-binding protein, Cdc13p. In gbp2-deleted cells, however, the telomere length and telomere position effect are not affected. To elucidate the role of Gbp2p in telomere function, a yeast two-hybrid system was used to identify its interacting proteins. Hrp1p was identified that interacted with Gbp2p and bound directly in vitro. Hrp1p is a nuclear polyadenylated RNA-binding protein involving in the RNA processing. Mutations on both GBP2 and HRP1 caused growth defect, further supports the interactions between these two proteins. However, mutations on either GBP2 and/or HRP1 did not affect telomere length, suggesting that these two genes are not involved in telomere length regulation. The silencing loci of yeast, including telomere silencing locus, were affected differently in gbp2 hrp1 mutants. These effects were not caused by RNA processing since the localization of mRNA or the level of several mRNAs were not affected in gbp2 and/or hrp1 mutants. Together, our results define a novel role of Gbp2 and Hrp1p in modulating silencing loci of yeast cells.
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