Biology subjects

Lydall, D.

Publications and source records attributed to Lydall, D..

3 recordsLinked to original sources

bioRxiv2018

Vps74 connects the Golgi apparatus and telomeres in Saccharomyces cerevisiae

In mammalian cell culture, the Golgi apparatus fragment upon DNA damage. GOLPH3, a Golgi component, is a phosphorylation target of DNA-PK after DNA damage and contributes to Golgi fragmentation. The function of the yeast (Saccharomyces cerevisiae) ortholog of GOLPH3, Vps74, in the DNA damage response has been little studied, although genome-wide screens suggested a role at telomeres. In this study we investigated the role of Vps74 at telomeres and in the DNA damage response. We show that Vps74 decreases the fitness of telomere defective cdc13-1 cells and contributes to the fitness of yku70{Delta} cells. Importantly, loss of Vps74 in yku70{Delta} cells exacerbates the temperature dependent growth defects of these cells in a Chk1 and Mec1-dependent manner. Furthermore, Exo1 reduces fitness of vps74{Delta} yku70{Delta} cells suggesting that ssDNA contributes to the fitness defects of vps74{Delta} yku70{Delta} cells. Systematic genetic interaction analysis of vps74{Delta}, yku70{Delta} and yku70{Delta} vps74{Delta} cells suggests that vps74{Delta} causes a milder but similar defect to that seen in yku70{Delta} cells. vps74{Delta} cells have slightly shorter telomeres and loss of VPS74 in yku70{Delta} or mre11{Delta} cells further shortens the telomeres of these cells. Interestingly, loss of Vps74 leads to increased levels of Stn1, a partner of Cdc13 in the CST telomere capping complex. Overexpression of Stn1 was previously shown to cause telomere shortening, suppression of cdc13-1 and enhancement of yku70{Delta} growth defects, suggesting that increased levels of Stn1 may be the route by which Vps74 affects telomere function. These results establish Vps74 as a novel regulator of telomere biology.

genetics↗

bioRxiv2018

A critical role for Dna2 at unwound telomeres

Dna2 is a nuclease and helicase that functions redundantly with other proteins in Okazaki fragment processing, double strand break (DSB) resection and checkpoint kinase activation. Dna2 is an essential enzyme, required for yeast and mammalian cell viability. Here we report that numerous mutations affecting the DNA damage checkpoint suppress dna2{Delta} lethality in Saccharomyces cerevisiae. dna2{Delta} cells are also suppressed by deletion of helicases, PIF1 and MPH1, and by deletion of POL32, a subunit of DNA polymerase {delta}. All dna2{Delta} cells are temperature sensitive, have telomere length defects, and low levels of telomeric 3 single stranded DNA (ssDNA). Interestingly, Rfa1, a subunit of the major ssDNA binding protein RPA, and the telomere specific ssDNA binding protein Cdc13, often co-localize in dna2{Delta} cells. This suggests that telomeric defects often occur in dna2{Delta} cells. There are several plausible explanations for why the most critical function of Dna2 is at telomeres. Telomeres modulate the DNA damage response (DDR) at chromosome ends, inhibiting resection, ligation and cell cycle arrest. We suggest that Dna2 nuclease activity contributes to modulating the DNA damage response at telomeres by removing telomeric C-rich ssDNA and thus preventing checkpoint activation.

genetics↗

bioRxiv2017

Systematic analysis of the effects of the DNA damage response network in telomere defective budding yeast

Functional telomeres are critically important to eukaryotic genetic stability. Budding yeast is a powerful model organism for genetic analysis and yeast telomeres are maintained by very similar mechanisms to human telomeres. Scores of proteins and pathways are known to affect telomere function. Here, we report a series of related genome-wide genetic interaction screens performed on budding yeast cells with acute or chronic telomere defects. We examined genetic interactions in cells defective in Cdc13 and Stn1, affecting two components of CST, a single stranded DNA (ssDNA) binding complex that binds telomeric DNA. We investigated genetic interactions in cells with defects in Rfa3, affecting the major ssDNA binding protein, RPA, which has overlapping functions with CST at telomeres. We also examined genetic interactions in cells lacking EXO1 or RAD9, affecting different aspects of the DNA damage response in a cdc13-1 background. Comparing fitness profiles across the data sets allows us build up a picture of the specific responses to different types of dysfunctional telomeres. Our results show that there is no universal response to telomere defects. To help others engage with the large volumes of data we make the data available via two interactive web-based tools: Profilyzer and DIXY. Among numerous genetic interactions we found the chk1{Delta} mutation improved fitness of cdc13-1 exo1{Delta} cells more than other checkpoint mutations (ddc1{Delta}, rad9{Delta}, rad17{Delta}, rad24{Delta}), whereas in cdc13-1 cells the effects of all checkpoint mutations were similar. We find that Chk1 stimulates resection at defective telomeres, revealing a new role for Chk1 in the eukaryotic DNA damage response network.

genetics↗