Journal of Biochemistry Advance Access originally published online on May 18, 2009
Journal of Biochemistry 2009 146(3):327-335; doi:10.1093/jb/mvp074
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DNA Helicase Activity in Purified Human RECQL4 Protein
1Ibaraki University, 2-1-1 Bunkyo, Mito, Ibaraki 310-8512; and 2Mitsubishi Kagaku Institute of Life Sciences (MITILS), 11 Minamiooya, Machida, Tokyo 194-8511, Japan
*To whom correspondence should be addressed. Tel/Fax: +81-29-228-8439, E-mail: ishimi{at}mx.ibaraki.ac.jp
Received March 10, 2009; Accepted May 3, 2009
| Abstract |
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Human RECQL4 protein was expressed in insect cells using a baculovirus protein expression system and it was purified to near homogeneity. The protein sedimented at a position between catalase (230 kDa) and ferritin (440 kDa) in glycerol gradient centrifugation, suggesting that it forms homo-multimers. Activity to displace annealed 17-mer oligonucleotide in the presence of ATP was co-sedimented with hRECQL4 protein. In ion-exchange chromatography, both DNA helicase activity and single-stranded DNA-dependent ATPase activity were co-eluted with hRECQL4 protein. The requirements of ATP and Mg for the helicase activity were different from those for the ATPase activity. The data suggest that the helicase migrates on single-stranded DNA in a 3'–5' direction. These results suggest that the hRECQL4 protein exhibits DNA helicase activity.
Key Words: DNA helicase, DNA replication, RecQ helicase, ATPase, Rothmund–Thomson syndrome
Abbreviations: WRN, Werner's syndrome; MCM, minichromosome maintenance; Sld2, synthetic lethality with dpbll-12