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Title: Two distinct mechanisms of Topoisomerase 1-dependent mutagenesis in yeast. Author: Cho JE, Kim N, Li YC, Jinks-Robertson S. Journal: DNA Repair (Amst); 2013 Mar 01; 12(3):205-11. PubMed ID: 23305949. Abstract: Topoisomerase 1 (Top1) resolves transcription-associated supercoils by generating transient single-strand breaks in DNA. Top1 activity in yeast is a major source of transcription-associated mutagenesis, generating a distinctive mutation signature characterized by deletions in short, tandem repeats. A similar signature is associated with the persistence of ribonucleoside monophosphates (rNMPs) in DNA, and it also depends on Top1 activity. There is only partial overlap, however, between Top1-dependent deletion hotspots identified in highly transcribed DNA and those associated with rNMPs, suggesting the existence of both rNMP-dependent and rNMP-independent events. Here, we present genetic studies confirming that there are two distinct types of hotspots. Data suggest a novel model in which rNMP-dependent hotspots are generated by sequential Top1 reactions and are consistent with rNMP-independent hotspots reflecting processing of a trapped Top1 cleavage complex.[Abstract] [Full Text] [Related] [New Search]