Laboratory of Molecular Gerontology, Biomedical Research Center, 251 Bayview Boulevard, National Institute on Aging, NIH, Baltimore, MD 21224, USA.
Nucleic Acids Res. 2012 Aug;40(14):6632-48. doi: 10.1093/nar/gks349. Epub 2012 Apr 28.
Bacteria and yeast possess one RecQ helicase homolog whereas humans contain five RecQ helicases, all of which are important in preserving genome stability. Three of these, BLM, WRN and RECQL4, are mutated in human diseases manifesting in premature aging and cancer. We are interested in determining to which extent these RecQ helicases function cooperatively. Here, we report a novel physical and functional interaction between BLM and RECQL4. Both BLM and RECQL4 interact in vivo and in vitro. We have mapped the BLM interacting site to the N-terminus of RECQL4, comprising amino acids 361-478, and the region of BLM encompassing amino acids 1-902 interacts with RECQL4. RECQL4 specifically stimulates BLM helicase activity on DNA fork substrates in vitro. The in vivo interaction between RECQL4 and BLM is enhanced during the S-phase of the cell cycle, and after treatment with ionizing radiation. The retention of RECQL4 at DNA double-strand breaks is shortened in BLM-deficient cells. Further, depletion of RECQL4 in BLM-deficient cells leads to reduced proliferative capacity and an increased frequency of sister chromatid exchanges. Together, our results suggest that BLM and RECQL4 have coordinated activities that promote genome stability.
细菌和酵母只拥有一个 RecQ 解旋酶同源物，而人类则含有五个 RecQ 解旋酶，它们在维持基因组稳定性方面都很重要。其中三种，BLM、WRN 和 RECQL4，在表现出早老症和癌症的人类疾病中发生突变。我们有兴趣确定这些 RecQ 解旋酶在多大程度上协同发挥作用。在这里，我们报告了 BLM 和 RECQL4 之间的一种新的物理和功能相互作用。BLM 和 RECQL4 均可在体内和体外相互作用。我们将 BLM 的相互作用位点映射到 RECQL4 的 N 端，包含氨基酸 361-478，而包含氨基酸 1-902 的 BLM 区域与 RECQL4 相互作用。RECQL4 特异性地刺激 BLM 在体外 DNA 叉底物上的解旋酶活性。RECQL4 和 BLM 之间的体内相互作用在细胞周期的 S 期以及电离辐射处理后增强。BLM 缺陷细胞中 RECQL4 在 DNA 双链断裂处的保留时间缩短。此外，BLM 缺陷细胞中 RECQL4 的耗竭导致增殖能力降低和姐妹染色单体交换频率增加。总之，我们的结果表明 BLM 和 RECQL4 具有协调的活动，可促进基因组稳定性。
