The Q motif of fanconi anemia group J protein (FANCJ) DNA helicase regulates its dimerization, DNA binding, and DNA repair function

Yuliang Wu, Joshua A. Sommers, Jason A. Loiland, Hiroyuki Kitao, Jochen Kuper, Caroline Kisker, Robert M. Brosh

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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.

Original languageEnglish
Pages (from-to)21699-21716
Number of pages18
JournalJournal of Biological Chemistry
Volume287
Issue number26
DOIs
Publication statusPublished - Jun 22 2012

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All Science Journal Classification (ASJC) codes

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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