title: Catalytic strand separation by RECQ1 is required for RPA-mediated response to replication stress.
abstract: Three (BLM, WRN, and RECQ4) of the five human RecQ helicases are linked to genetic disorders characterized by genomic instability, cancer, and accelerated aging [1]. RECQ1, the first human RecQ helicase discovered [2-4] and the most abundant [5], was recently implicated in breast cancer [6, 7]. RECQ1 is an ATP-dependent DNA-unwinding enzyme (helicase) [8, 9] with roles in replication [10-12] and DNA repair [13-16]. RECQ1 is highly expressed in various tumors and cancer cell lines (for review, see [17]), and its suppression reduces cancer cell proliferation [14], suggesting a target for anti-cancer drugs. RECQ1's assembly state plays a critical role in modulating its helicase, branch migration (BM), or strand annealing [18, 19]. The crystal structure of truncated RECQ1 [20, 21] resembles that of E. coli RecQ [22] with two RecA-like domains, a RecQ-specific zinc-binding domain and a winged-helix domain, the latter implicated in DNA strand separation and oligomer formation. In addition, a conserved aromatic loop (AL) is important for DNA unwinding by bacterial RecQ [23, 24] and truncated RECQ1 helicases [21]. To better understand the roles of RECQ1, two AL mutants (W227A and F231A) in full-length RECQ1 were characterized biochemically and genetically. The RECQ1 mutants were defective in helicase or BM but retained DNA binding, oligomerization, ATPase, and strand annealing. RECQ1-depleted HeLa cells expressing either AL mutant displayed reduced replication tract length, elevated dormant origin firing, and increased double-strand breaks that could be suppressed by exogenously expressed replication protein A (RPA). Thus, RECQ1 governs RPA's availability in order to maintain normal replication dynamics, suppress DNA damage, and preserve genome homeostasis.
authors.affiliation: Laboratory of Molecular Gerontology, National Institute on Aging, NIH, NIH Biomedical Research Center, 251 Bayview Boulevard, Baltimore, MD 21224, USA.
authors.forename: Taraswi
authors.initials: T
authors.lastname: Banerjee
authors.affiliation: Laboratory of Molecular Gerontology, National Institute on Aging, NIH, NIH Biomedical Research Center, 251 Bayview Boulevard, Baltimore, MD 21224, USA.
authors.forename: Joshua A
authors.initials: JA
authors.lastname: Sommers
authors.affiliation: Laboratory of Molecular Gerontology, National Institute on Aging, NIH, NIH Biomedical Research Center, 251 Bayview Boulevard, Baltimore, MD 21224, USA.
authors.forename: Jing
authors.initials: J
authors.lastname: Huang
authors.affiliation: Laboratory of Molecular Gerontology, National Institute on Aging, NIH, NIH Biomedical Research Center, 251 Bayview Boulevard, Baltimore, MD 21224, USA.
authors.forename: Michael M
authors.initials: MM
authors.lastname: Seidman
authors.affiliation: Laboratory of Molecular Gerontology, National Institute on Aging, NIH, NIH Biomedical Research Center, 251 Bayview Boulevard, Baltimore, MD 21224, USA. Electronic address: broshr@mail.nih.gov.
authors.forename: Robert M
authors.initials: RM
authors.lastname: Brosh
mesh_terms: D045744:Cell Line, Tumor; D002478:Cells, Cultured; D004247:DNA / Q000235:genetics / Q000378:metabolism; D004249:DNA Damage; D004260:DNA Repair; D004261:DNA Replication / Q000235:genetics / Q000502:physiology*; D042822:Genomic Instability; D006801:Humans; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D053484:RecQ Helicases / Q000235:genetics* / Q000378:metabolism*; D051716:Replication Protein A / Q000378:metabolism; D013312:Stress, Physiological / Q000235:genetics / Q000502:physiology*; D013379:Substrate Specificity
chemical_list: D051716:Replication Protein A; D004247:DNA; C506725:RECQL protein, human; C506731:RECQL4 protein, human; D053484:RecQ Helicases