The CDC13 gene encodes a protein that binds to the G-rich single-strand at yeast telomeres, and serves as a regulator of telomere replication. Cdc13 interacts with Est1 and DNA polymerase alpha, and cells carrying the temperature-sensitive allele cdc13-1 cannot complete telomere replication at the restrictive temperature and possess long telomeres. We attempted to isolate and characterize genes that interact with CDC13, in order to clarify the molecular mechanisms of telomere replication. A STM1 cDNA was isolated in a two-hybrid screen using CDC13 as a bait. The temperature-sensitive growth phenotype and the alteration in telomere size in cdc13-1 cells were corrected by introduction of the STM1 gene on a multicopy vector, but the extended G-rich single-strand overhangs which are also characteristic in the cdc13-1 mutant were not affected. Furthermore, we found that multiple copies of SGS1, a gene encoding a helicase that can unwind guanine quadruplexes, inhibited suppression of the cdc13-1 phenotype by STM1. We also demonstrate that a fusion protein consisting of the N-terminal region of Cdc13 and the C-terminal region of Stm1 (which shows similarity to the beta-subunit of the telomere binding complex in Oxytricha) could complement a cdc13 disruptant. Although STM1 itself is not essential for telomere replication, our findings suggest that STM1 genetically interacts with CDC13 to maintain telomere structure.
"The G-rich single-strand 3′ overhang that constitutes the substrate for telomerase can adopt unusual secondary structures. In particular, it may fold into very stable G-quadruplexes or G4-DNA (Hayashi and Murakami, 2002; Zhang et al., 2010; Smith et al., 2011). These structures may constitute an obstacle for telomere replication, telomerase recruitment and telomere elongation by telomerase (Paeschke et al., 2010). "
[Show abstract][Hide abstract] ABSTRACT: Telomere elongation by telomerase involves sequential steps that must be highly coordinated to ensure the maintenance of telomeres at a proper length. Telomerase is delivered to telomere ends, where it engages single-strand DNA end as a primer, elongates it, and dissociates from the telomeres via mechanism that is likely coupled to the synthesis of the complementary C-strand. In , the telomeric G-overhang bound Cdc13 acts as a platform for the recruitment of several factors that orchestrate timely transitions between these steps. In this review, we focus on some unresolved aspects of telomerase recruitment and on the mechanisms that regulate telomere elongation by telomerase after its recruitment to chromosome ends. We also highlight the key regulatory modifications of Cdc13 that promote transitions between the steps of telomere elongation.
Frontiers in Oncology 02/2013; 3:39. DOI:10.3389/fonc.2013.00039
"Interestingly, Est1 could convert the single-stranded telomeric DNA to a G quadruplex structure to prevent telomerase RNA TLC1 from annealing at the internal part of the single-stranded telomeric DNA, thereby positioning telomerase to the proximal 3 0 terminus (Zhang et al., 2010). In agreement with these results, Cdc13 interacts in a two-hybrid screen with a G-quadruplex-binding protein called Smt1, which suppresses the ts phenotype of cdc13-1 when overexpressed (Hayashi and Murakami, 2002). "
[Show abstract][Hide abstract] ABSTRACT: Telomere protection in budding yeast requires the heterotrimer named CST (for Cdc13-Stn1-Ten1). Recent data show that CST components are conserved and required for telomere stability in a wide range of eukaryotes, even those utilizing the shelterin complex to protect their telomeres. A common function of these proteins might be to stimulate priming at the C-strand gap that remains after telomerase elongation, replication termination, and terminal processing. In light of the budding yeast situation, another conserved function of CST might well be the regulation of telomerase. The cohabitation at telomeres of CST and shelterin components highlights the complexity of telomere biology.
"The Saccharomyces cerevisiae gene STM1 and its encoded protein Stm1p have been implicated in myriad biological processes, including apoptosis, cell-cycle regulation, telomere biosynthesis, cell-life span regulation, messenger RNA (mRNA) degradation and nutritional stress responses (1–11). However, it is not inherently obvious how a single protein is able to influence so many different biological processes. "
[Show abstract][Hide abstract] ABSTRACT: Stm1p is a Saccharomyces cerevisiae protein that is primarily associated with cytosolic 80S ribosomes and polysomes. Several lines of evidence suggest that Stm1p plays a role in translation under nutrient stress conditions, although its mechanism of action is not yet known. In this study, we show that yeast lacking Stm1p (stm1Delta) are hypersensitive to the translation inhibitor anisomycin, which affects the peptidyl transferase reaction in translation elongation, but show little hypersensitivity to other translation inhibitors such as paromomycin and hygromycin B, which affect translation fidelity. Ribosomes isolated from stm1Delta yeast have intrinsically elevated levels of eukaryotic elongation factor 3 (eEF3) associated with them. Overexpression of eEF3 in cells lacking Stm1p results in a growth defect phenotype and increased anisomycin sensitivity. In addition, ribosomes with increased levels of Stm1p exhibit decreased association with eEF3. Taken together, our data indicate that Stm1p plays a complementary role to eEF3 in translation.
Nucleic Acids Research 09/2009; 37(18):6116-25. DOI:10.1093/nar/gkp645 · 9.11 Impact Factor
Data provided are for informational purposes only. Although carefully collected, accuracy cannot be guaranteed. The impact factor represents a rough estimation of the journal's impact factor and does not reflect the actual current impact factor. Publisher conditions are provided by RoMEO. Differing provisions from the publisher's actual policy or licence agreement may be applicable.