title: The Q motif of Fanconi anemia group J protein (FANCJ) DNA helicase regulates its dimerization, DNA binding, and DNA repair function.
abstract: The Q motif, conserved in a number of RNA and DNA helicases, is proposed to be important for ATP binding based on structural data, but its precise biochemical functions are less certain. FANCJ encodes a Q motif DEAH box DNA helicase implicated in Fanconi anemia and breast cancer. A Q25A mutation of the invariant glutamine in the Q motif abolished its ability to complement cisplatin or telomestatin sensitivity of a fancj null cell line and exerted a dominant negative effect. Biochemical characterization of the purified recombinant FANCJ-Q25A protein showed that the mutation disabled FANCJ helicase activity and the ability to disrupt protein-DNA interactions. FANCJ-Q25A showed impaired DNA binding and ATPase activity but displayed ATP binding and temperature-induced unfolding transition similar to FANCJ-WT. Size exclusion chromatography and sedimentation velocity analyses revealed that FANCJ-WT existed as molecular weight species corresponding to a monomer and a dimer, and the dimeric form displayed a higher specific activity for ATPase and helicase, as well as greater DNA binding. In contrast, FANCJ-Q25A existed only as a monomer, devoid of helicase activity. Thus, the Q motif is essential for FANCJ enzymatic activity in vitro and DNA repair function in vivo.
authors.affiliation: Laboratory of Molecular Gerontology, National Institutes of Health Biomedical Research Center, NIA, Baltimore, Maryland 21224, USA.
authors.forename: Yuliang
authors.initials: Y
authors.lastname: Wu
authors.forename: Joshua A
authors.initials: JA
authors.lastname: Sommers
authors.forename: Jason A
authors.initials: JA
authors.lastname: Loiland
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Kitao
authors.forename: Jochen
authors.initials: J
authors.lastname: Kuper
authors.forename: Caroline
authors.initials: C
authors.lastname: Kisker
authors.forename: Robert M
authors.initials: RM
authors.lastname: Brosh
mesh_terms: D000251:Adenosine Triphosphatases / Q000737:chemistry; D000255:Adenosine Triphosphate / Q000737:chemistry; D020816:Amino Acid Motifs; D000818:Animals; D050976:Basic-Leucine Zipper Transcription Factors / Q000235:genetics* / Q000378:metabolism*; D002384:Catalysis; D002460:Cell Line; D002470:Cell Survival; D002645:Chickens; D002845:Chromatography / Q000379:methods; D004260:DNA Repair; D019281:Dimerization; D051856:Fanconi Anemia Complementation Group Proteins / Q000235:genetics* / Q000378:metabolism*; D005990:Glycerol / Q000494:pharmacology; D006367:HeLa Cells; D006801:Humans; D006868:Hydrolysis; D007700:Kinetics; D008954:Models, Biological; D008957:Models, Genetic; D016296:Mutagenesis; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D010080:Oxazoles / Q000494:pharmacology; D011489:Protein Denaturation; D011994:Recombinant Proteins / Q000378:metabolism; D013696:Temperature
chemical_list: C102108:BACH1 protein, human; D050976:Basic-Leucine Zipper Transcription Factors; D051856:Fanconi Anemia Complementation Group Proteins; D010080:Oxazoles; D011994:Recombinant Proteins; C431888:telomestatin; D000255:Adenosine Triphosphate; D000251:Adenosine Triphosphatases; D005990:Glycerol