Department of Molecular Biology, The Scripps Research Institute, La Jolla, California, USA.
Mol Cell Biol. 2012 Jan;32(2):276-87. doi: 10.1128/MCB.06184-11. Epub 2011 Nov 7.
Of the five human RecQ family helicases, RecQ4, BLM, and WRN suppress distinct genome instability-linked diseases with severe phenotypes, often with indeterminate etiologies. Here, we functionally define Hrq1, a novel orthologue of RecQ4 from fission yeast. Biochemical analysis of Hrq1 reveals a DEAH box- and ATP-dependent 3'-5' helicase activity on various DNA substrates, including bubbles but not blunt duplexes, characteristic of the RecQ family. Cells lacking Hrq1 suffer spontaneous genomic instability and, consequently, require homologous recombination repair and the DNA damage checkpoint for viability. Hrq1 supports the nucleotide excision repair of DNA damage caused by the chemotherapeutic agent cisplatin and, in certain genetic contexts, UV light. Genetic epistasis analyses reveal that Hrq1 acts parallel to the PCNA/Ubc13/Mms2-dependent postreplication repair (PRR) pathway. Thus, in hrq1Δ cells, lesions are channeled through the PRR pathway, yielding hyper-recombinant and mutator phenotypes; analogous defects may underlie the genetic instability and diseases associated with RecQ4 dysfunction.
在人类的五个 RecQ 家族解旋酶中，RecQ4、BLM 和 WRN 可抑制具有严重表型的不同与基因组不稳定性相关的疾病，其病因通常不确定。在这里，我们从裂殖酵母中功能性地定义了一个 RecQ4 的新直系同源物 Hrq1。对 Hrq1 的生化分析揭示了它在各种 DNA 底物上具有 DEAH 盒和 ATP 依赖性的 3'-5'解旋酶活性，包括泡但不包括平末端双链体，这是 RecQ 家族的特征。缺乏 Hrq1 的细胞会自发地发生基因组不稳定性，因此需要同源重组修复和 DNA 损伤检查点来维持其生存。Hrq1 支持由化疗药物顺铂引起的 DNA 损伤的核苷酸切除修复，并且在某些遗传背景下还支持 UV 光的修复。遗传上位性分析表明，Hrq1 与 PCNA/Ubc13/Mms2 依赖性复制后修复（PRR）途径平行作用。因此，在 hrq1Δ 细胞中，损伤通过 PRR 途径进行传递，导致高重组和突变表型；类似的缺陷可能是 RecQ4 功能障碍相关的遗传不稳定性和疾病的基础。
