Using the S. cerevisiae Stn1 telomere capping protein to dissect downstream responses of the S phase checkpoint

Abstract

In the budding yeast S. cerevisiae, Stn1 is an essential protein that caps chromosome ends, and facilitates telomere replication. Previous work in our lab has shown that increasing the levels of Stn1 makes cells extremely sensitive to the replication inhibitors hydroxyurea (HU) and methyl‐methane sulfonate (MMS). Remarkably, this sensitivity corresponds with overproduced Stn1 abrogating most aspects of the S phase checkpoint, including destabilization of replication forks, de‐repression of late replication origins, and causing cells to arrest with elongated mitotic spindles. The Rad53 checkpoint kinase is activated normally in Stn1 overproducing cells, indicating Stn1 is impacting checkpoint responses downstream of the checkpoint signal transduction pathway. These observations indicate that Stn1 overproduction provides a unique reagent to probe downstream aspects of Rad53 function, and we are therefore analyzing the mechanism and genetic requirements by which Stn1 shuts down execution of the S phase checkpoint pathway. This work was funded in part by the NSF, grant number 1024792 awarded to Connie Nugent.