Two pathways for removal of nonhomologous DNA ends during double-strand break repair in Saccharomyces cerevisiae.
During repair of a double-strand break (DSB) by gene conversion, one or both 3' ends of the DSB invade a homologous donor sequence and initiate new DNA synthesis. The use of the invading DNA strand as a primer for new DNA synthesis requires that any nonhomologous bases at the 3' end be removed. We have previously shown that removal of a 3' nonhomologous tail in Saccharomyces cerevisiae depends on the nucleotide excision repair endonuclease Rad1/Rad10, and also on the mismatch repair proteins Msh2 and Msh3. We now report that these four proteins are needed only when the nonhomologous ends of recombining DNA are 30 nucleotides (nt) long or longer. An additional protein, the helicase Srs2, is required for the RAD1-dependent removal of long 3' tails. We suggest that Srs2 acts to extend and stabilize the initial nascent joint between the invading single strand and its homolog. 3' tails shorter than 30 nt are removed by another mechanism that depends at least in part on the 3'-to-5' proofreading activity of DNA polymerase delta.
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Rosenstiel Center and Department of Biology, Brandeis University, Waltham, Massachusetts 02254-9110, USA.
Haber
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JE
D004249:DNA Damage; D004265:DNA Helicases / Q000378:metabolism; D004258:DNA Polymerase III / Q000378:metabolism; D004260:DNA Repair; D045643:DNA Repair Enzymes; D004271:DNA, Fungal / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism; D004720:Endonucleases / Q000378:metabolism; D005656:Fungal Proteins / Q000378:metabolism; D005785:Gene Conversion; D051718:MutS Homolog 2 Protein; D000074081:MutS Homolog 3 Protein; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins
D004271:DNA, Fungal; D004268:DNA-Binding Proteins; D005656:Fungal Proteins; C081696:MSH3 protein, S cerevisiae; D000074081:MutS Homolog 3 Protein; D029701:Saccharomyces cerevisiae Proteins; C061376:SRS2 protein, S cerevisiae; D004258:DNA Polymerase III; D004720:Endonucleases; C069266:RAD1 protein, S cerevisiae; C489751:MSH2 protein, S cerevisiae; D051718:MutS Homolog 2 Protein; D004265:DNA Helicases; D045643:DNA Repair Enzymes