title: Mismatch recognition protein MutSbeta does not hijack (CAG)n hairpin repair in vitro.
abstract: CAG repeats form stable hairpin structures, which are believed to be responsible for CAG repeat expansions associated with certain human neurological diseases. Human cells possess an accurate DNA hairpin repair system that prevents expansion of disease-associated CAG repeats. Based on transgenic animal studies, it is suggested that (CAG)(n) expansion is caused by abnormal binding of the MutSbeta mismatch recognition protein to (CAG)(n) hairpins, leading to hijacking mismatch repair function during (CAG)(n) hairpin repair. We demonstrate here that MutSbeta displays identical biochemical and biophysical activities (including ATP-provoked conformational change, ATPase, ATP binding, and ADP binding) when interacting with a (CAG)(n) hairpin and a mismatch. More importantly, our in vitro functional hairpin repair assays reveal that excess MutSbeta does not inhibit (CAG)(n) hairpin repair in HeLa nuclear extracts. Evidence presented here provides a novel view as to whether or not MutSbeta is involved in CAG repeat instability in humans.
authors.affiliation: Graduate Center for Toxicology, Markey Cancer Center, University of Kentucky College of Medicine, Lexington, Kentucky 40536, USA.
authors.forename: Lei
authors.initials: L
authors.lastname: Tian
authors.forename: Caixia
authors.initials: C
authors.lastname: Hou
authors.forename: Keli
authors.initials: K
authors.lastname: Tian
authors.forename: Nathaniel C
authors.initials: NC
authors.lastname: Holcomb
authors.forename: Liya
authors.initials: L
authors.lastname: Gu
authors.forename: Guo-Min
authors.initials: GM
authors.lastname: Li
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism; D001483:Base Sequence; D053843:DNA Mismatch Repair; D004268:DNA-Binding Proteins / Q000378:metabolism*; D017353:Gene Deletion; D006367:HeLa Cells; D006801:Humans; D006868:Hydrolysis; D051718:MutS Homolog 2 Protein / Q000378:metabolism*; D000074081:MutS Homolog 3 Protein; D016254:Mutagenesis, Insertional; D009690:Nucleic Acid Conformation; D009692:Nucleic Acid Heteroduplexes / Q000378:metabolism; D009841:Oligonucleotides / Q000737:chemistry* / Q000378:metabolism*; D011485:Protein Binding
chemical_list: D004268:DNA-Binding Proteins; C078444:MSH3 protein, human; D000074081:MutS Homolog 3 Protein; D009692:Nucleic Acid Heteroduplexes; D009841:Oligonucleotides; D000251:Adenosine Triphosphatases; C497172:MSH2 protein, human; D051718:MutS Homolog 2 Protein