title: Mu transpososome and RecBCD nuclease collaborate in the repair of simple Mu insertions.
abstract: The genome of transposable phage Mu is packaged as a linear segment, flanked by several hundred base pairs of non-Mu DNA. The linear ends are held together and protected from nucleases by the phage N protein. After transposition into the Escherichia coli chromosome, the flanking DNA (FD) is degraded, and the 5-bp gaps left in the target are repaired to generate a simple Mu insertion. Our study provides insights into this repair pathway. The data suggest that the first event in repair is removal of the FD by the RecBCD exonuclease, whose entry past the N-protein block is licensed by the transpososome. In vitro experiments reveal that, when RecBCD is allowed entry into the FD, it degrades this DNA until it arrives at the transpososome, which presents a barrier for further RecBCD movement. RecBCD action is required for stimulating endonucleolytic cleavage within the transpososome-protected DNA, leaving 4-nt flanks outside both Mu ends. This end product of collaboration between the transpososome and RecBCD resembles the intermediate products of Tn7 and retroviral and retrotransposon transposition, and may hint at a common gap-repair mechanism in these diverse transposons.
authors.affiliation: Department of Molecular Biosciences and Institute of Cellular and Molecular Biology, The University of Texas at Austin, Austin, TX 78712.
authors.forename: Wonyoung
authors.initials: W
authors.lastname: Choi
authors.affiliation: Department of Molecular Biosciences and Institute of Cellular and Molecular Biology, The University of Texas at Austin, Austin, TX 78712.
authors.forename: Sooin
authors.initials: S
authors.lastname: Jang
authors.affiliation: Department of Molecular Biosciences and Institute of Cellular and Molecular Biology, The University of Texas at Austin, Austin, TX 78712 rasika@austin.utexas.edu.
authors.forename: Rasika M
authors.initials: RM
authors.lastname: Harshey
mesh_terms: D019943:Amino Acid Substitution; D010583:Bacteriophage mu / Q000235:genetics* / Q000378:metabolism*; D004260:DNA Repair; D004251:DNA Transposable Elements / Q000235:genetics*; D004279:DNA, Viral / Q000235:genetics / Q000378:metabolism; D048168:Escherichia coli K12 / Q000235:genetics / Q000378:metabolism / Q000821:virology; D043211:Exodeoxyribonuclease V / Q000378:metabolism*; D057809:HEK293 Cells; D006801:Humans; D008954:Models, Biological; D016297:Mutagenesis, Site-Directed; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D013045:Species Specificity; D019895:Transposases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D014764:Viral Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism
chemical_list: D004251:DNA Transposable Elements; D004279:DNA, Viral; D014764:Viral Proteins; C114697:mu transposase; D019895:Transposases; D043211:Exodeoxyribonuclease V
keywords: conservative integration; nonreplicative transposition