Conserved helicase domain of human RecQ4 is required for strand annealing-independent DNA unwinding |
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| Authors: | Marie L. Rossi Avik K. Ghosh Tomasz Kulikowicz Deborah L. Croteau Vilhelm A. Bohr |
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| Affiliation: | 1. Institute of Medical Radiation Biology, University of Duisburg-Essen Medical School, Essen, Germany;2. Graduate School of Nanobioscience and Advanced Medical Research Center, Yokohama City University, Yokohama, Japan;1. Department of Biochemistry, University of Iowa, Iowa City, IA 52242, USA;2. Department of Pharmaceutical Sciences and Experimental Therapeutics, Division of Medicinal and Natural Products Chemistry, University of Iowa, Iowa City, IA 52242, USA;1. Key Laboratory of Animal Genetics, Breeding and Reproduction in Plateau Mountainous Region, Ministry of Education, College of Animal Science, Guizhou University, Guiyang 550025, Guizhou, China;2. Guizhou Key Laboratory of Animal Genetics, Breeding and Reproduction, College of Animal Science, Guizhou University, Guiyang 550025, Guizhou, China;3. Provincial Key Laboratory for Agricultural Pest Management of Mountainous Region, Guizhou University, Guiyang 550025, Guizhou, China;3. Structural Biology Laboratory, Elettra-Sincrotrone Trieste, 34149 Basovizza, Trieste, Italy;4. Dipartimento di Scienze della Vita, Università degli Studi di Trieste, 34127 Trieste, Italy |
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| Abstract: | Humans have five members of the well conserved RecQ helicase family: RecQ1, Bloom syndrome protein (BLM), Werner syndrome protein (WRN), RecQ4, and RecQ5, which are all known for their roles in maintaining genome stability. BLM, WRN, and RecQ4 are associated with premature aging and cancer predisposition. Of the three, RecQ4's biological and cellular roles have been least thoroughly characterized. Here we tested the helicase activity of purified human RecQ4 on various substrates. Consistent with recent results, we detected ATP-dependent RecQ4 unwinding of forked duplexes. However, our results provide the first evidence that human RecQ4's unwinding is independent of strand annealing, and that it does not require the presence of excess ssDNA. Moreover, we demonstrate that a point mutation of the conserved lysine in the Walker A motif abolished helicase activity, implying that not the N-terminal portion, but the helicase domain is solely responsible for the enzyme's unwinding activity. In addition, we demonstrate a novel stimulation of RecQ4's helicase activity by replication protein A, similar to that of RecQ1, BLM, WRN, and RecQ5. Together, these data indicate that specific biochemical activities and protein partners of RecQ4 are conserved with those of the other RecQ helicases. |
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