Deciphering End Resection in Double-Strand Break repair in Saccharomyces cerevisiae

Double-strand breaks (DSBs) are highly cytotoxic DNA lesions that are usually repaired by two major mechanisms: non-homologous end joining (NHEJ) and homologous recombination (HR). HR is initiated by 5'-3' resection, generating 3' single stranded DNA tails coated by Replication protein A (RPA), which can be used in later steps for homology search and repair. The 5'-3' resection step is a critical determinant of repair pathway choice that commits cells to HR instead of NHEJ, and it's also required for DNA damage checkpoint activation. Studies in the budding yeast Saccharomyces cerevisiae have shown that the conserved Mre11-Rad50-Xrs2 (MRX) complex, together with Sae2, initiates end resection while more extensive processing of 5' strands requires the 5'-3' exonuclease Exo1, or the combined activities of the Sgs1 helicase and Dna2 endonuclease. In this thesis we will discuss the function of RPA and Sae2 based on our experimental observations. RPA is an essential eukaryotic single-stranded DNA binding protein with a central role in DNA metabolism. It has been shown in vitro that RPA directly participates in end resection by stimulating the Sgs1 helicase and Dna2 endonuclease. To invest