title: DNA repair by the cryptic endonuclease activity of Mu transposase.
abstract: Phage Mu transposes by two distinct pathways depending on the specific stage of its life cycle. A common strand transfer intermediate is resolved differentially in the two pathways. During lytic growth, the intermediate is resolved by replication of Mu initiated within the flanking target DNA; during integration of infecting Mu, it is resolved without replication, by removal and repair of DNA from a previous host that is still attached to the ends of the incoming Mu genome. We have discovered that the cryptic endonuclease activity reported for the isolated C-terminal domain of the transposase MuA [Wu Z, Chaconas G (1995) A novel DNA binding and nuclease activity in domain III of Mu transposase: Evidence for a catalytic region involved in donor cleavage. EMBO J 14:3835-3843], which is not observed in the full-length protein or in the assembled transpososome in vitro, is required in vivo for removal of the attached host DNA or "5'flap" after the infecting Mu genome has integrated into the E. coli chromosome. Efficient flap removal also requires the host protein ClpX, which is known to interact with the C-terminus of MuA to remodel the transpososome for replication. We hypothesize that ClpX constitutes part of a highly regulated mechanism that unmasks the cryptic nuclease activity of MuA specifically in the repair pathway.
authors.affiliation: Section of Molecular Genetics and Microbiology and Institute of Cellular and Molecular Biology, University of Texas at Austin, Austin, TX 78712, USA.
authors.forename: Wonyoung
authors.initials: W
authors.lastname: Choi
authors.forename: Rasika M
authors.initials: RM
authors.lastname: Harshey
mesh_terms: D000074183:ATPases Associated with Diverse Cellular Activities; D000251:Adenosine Triphosphatases / Q000378:metabolism; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D010583:Bacteriophage mu / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D004260:DNA Repair / Q000502:physiology*; D004261:DNA Replication / Q000502:physiology; D004720:Endonucleases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D049071:Endopeptidase Clp / Q000378:metabolism; D048168:Escherichia coli K12 / Q000235:genetics / Q000502:physiology / Q000821:virology; D029968:Escherichia coli Proteins / Q000378:metabolism; D008242:Lysogeny; D008954:Models, Biological; D018832:Molecular Chaperones / Q000378:metabolism; D016297:Mutagenesis, Site-Directed; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D019895:Transposases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D016662:Virus Integration / Q000502:physiology; D014779:Virus Replication / Q000502:physiology
chemical_list: D029968:Escherichia coli Proteins; D018832:Molecular Chaperones; D011994:Recombinant Proteins; C114697:mu transposase; D019895:Transposases; D004720:Endonucleases; D049071:Endopeptidase Clp; D000251:Adenosine Triphosphatases; C088072:ClpX protein, E coli; D000074183:ATPases Associated with Diverse Cellular Activities