George Tresa, Wen Qin, Griffiths Richard, Ganesh Anil, Meuth Mark, Sanders Cyril M
Institute for Cancer Studies, University of Sheffield, Beech Hill Road, Sheffield S10 2RX, UK.
Nucleic Acids Res. 2009 Oct;37(19):6491-502. doi: 10.1093/nar/gkp671. Epub 2009 Aug 21.
Pif-1 proteins are 5'-->3' superfamily 1 (SF1) helicases that in yeast have roles in the maintenance of mitochondrial and nuclear genome stability. The functions and activities of the human enzyme (hPif1) are unclear, but here we describe its DNA binding and DNA remodeling activities. We demonstrate that hPif1 specifically recognizes and unwinds DNA structures resembling putative stalled replication forks. Notably, the enzyme requires both arms of the replication fork-like structure to initiate efficient unwinding of the putative leading replication strand of such substrates. This DNA structure-specific mode of initiation of unwinding is intrinsic to the conserved core helicase domain (hPifHD) that also possesses a strand annealing activity as has been demonstrated for the RecQ family of helicases. The result of hPif1 helicase action at stalled DNA replication forks would generate free 3' ends and ssDNA that could potentially be used to assist replication restart in conjunction with its strand annealing activity.
Pif-1蛋白是5'→3'超家族1（SF1）解旋酶，在酵母中参与维持线粒体和核基因组的稳定性。人类酶（hPif1）的功能和活性尚不清楚，但在此我们描述了其DNA结合和DNA重塑活性。我们证明hPif1能特异性识别并解开类似于假定停滞复制叉的DNA结构。值得注意的是，该酶需要复制叉样结构的双臂来启动对此类底物假定的前导复制链的有效解旋。这种解旋起始的DNA结构特异性模式是保守的核心解旋酶结构域（hPifHD）所固有的，该结构域也具有链退火活性，正如RecQ解旋酶家族所证明的那样。hPif1解旋酶在停滞的DNA复制叉处作用的结果将产生游离的3'末端和单链DNA，这些可能与它的链退火活性一起用于协助复制重新启动。
