Reparo do DNA pela atividade críptica da endonuclease da Mu transposase

sexta-feira, fevereiro 19, 2010

DNA repair by the cryptic endonuclease activity of Mu transposase

Wonyoung Choi and Rasika M. Harshey1

+Author Affiliations

Section of Molecular Genetics and Microbiology and Institute of Cellular and Molecular Biology, University of Texas at Austin, Austin, TX 78712

Edited by Charles M. Radding, Yale University School of Medicine, New Haven, CT 06510, and approved December 23, 2009 (received for review November 2, 2009)


Phage Mu transposes by two distinct pathways depending on the specific stage of its life cycle. A common θ strand transfer intermediate is resolved differentially in the two pathways. During lytic growth, the θ 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. colichromosome. 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.

MuA transposase    Mu DNA transposition   ClpX    retroviral integration   post-integration repair


1To whom correspondence should be addressed.

Author contributions: W.C. and R.M.H. designed research; W.C. performed research; W.C. contributed new reagents/analytic tools; W.C. and R.M.H. analyzed data; and R.M.H. wrote the paper.

The authors declare no conflict of interest.

This article is a PNAS Direct Submission.

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