STM1, a gene which encodes a guanine quadruplex binding protein, interacts with CDC13 in Saccharomyces cerevisiae
Department of Molecular Oncology, Cancer Research Institute, Kanazawa University, 13-1 Takara-machi, Kanazawa, Ishikawa 920-0934, Japan. Molecular Genetics and Genomics
(Impact Factor: 2.73).
09/2002; 267(6):806-13. DOI: 10.1007/s00438-002-0712-3
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.
Available from: Dmitri Churikov
- "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). "
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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.
Available from: Michael Van Dyke
- "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. "
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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 (stm1Δ) 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 stm1Δ 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.
Available from: San-Yuan Huang
- "Stm1p binds quadruplex and triple helical nucleic acids (Frantz and Gilbert 1995; Nelson et al. 2000). It has been implicated in telomere structure maintenance (Hayashi and Murakami 2002) and signaling of apoptosis-like cell death (Ligr et al. 2001). Stm1p has a single RGG motif near the C terminus of the protein ( 234 NNRRGGRGARK 244 ). "
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ABSTRACT: Protein arginine methylation often modulates protein-protein interactions. To isolate a sufficient quantity of proteins enriched in methyl arginine(s) from natural sources for biochemical studies is laborious and difficult. We describe here an expression system that produces recombinant proteins that are enriched in omega-N(G),N(G)-asymmetry dimethylarginines. A yeast type I arginine methyltransferase gene (HMT1) is put on a plasmid under the control of the Escherichia coli methionine aminopeptidase promoter for constitutive expression. The protein targeted for post-translational modification is put on the same plasmid behind a T7 promoter for inducible expression of His(6)-tagged proteins. Sbp1p and Stm1p were used as model proteins to examine this expression system. The 13 arginines within the arginine-glycine-rich motif of Sbp1p and the RGG sequence near the C terminus of Stm1p were methylated. Unexpectedly, the arginine residue on the thrombin cleavage site (LVPRGS) of the fusion proteins can also be methylated by Hmt1p. Sbp1p and Sbp1p/hmt1 were covalently attached to solid supports for the isolation of interacting proteins. The results indicate that arginine methylation on Sbp1p exerts both positive and negative effects on protein-protein interaction.
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