PIF1 family DNA helicases suppress R-loop mediated genome instability at tRNA genes.
PIF1 family DNA helicases suppress R-loop mediated genome instability at tRNA genes.
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DOI：
10.1038/ncomms15025
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发表时间：
2017-04-21
影响因子：
16.6
通讯作者：
Zakian VA
中科院分区：
文献类型：
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作者：
Tran PLT;Pohl TJ;Chen CF;Chan A;Pott S;Zakian VA
酿酒酵母编码Pif1家族DNA解旋酶Pif1和Rrm3。Rrm3通过稳定的蛋白质复合物在tRNA基因（tdna）上促进DNA复制。我们确定了Pif1解旋酶的新作用：促进tdna的复制和抑制DNA损伤。Pif1结合多个tdna，这种结合在rrm3Δ细胞中更高。在pif1Δ rrm3Δ细胞中，tdna的复制中间体积累和DNA损伤高于rrm3Δ细胞。在没有这些解旋酶的情况下，破坏稳定的r环可以抑制tdna上的DNA损伤，而在r环稳定后，与tdna结合的Pif1和Rrm3增加。我们认为Rrm3和Pif1通过取代稳定的多蛋白转录复合物和去除r环来促进tdna上基因组的稳定性。因此，我们确定tdna是r -环介导的DNA损伤的新来源。由于tdna数量多，转录率高，因此tdna可能是基因组不稳定的一个重要来源。出芽酵母基因组编码两种Pif1家族解旋酶，Pif1和Rrm3，先前显示在维持端粒和基因组稳定性的其他方面具有不同的功能。在这里，作者确定了Pif1（和Rrm3）在促进DNA复制和抑制r环介导的tRNA基因DNA损伤中的作用。
Saccharomyces cerevisiae encodes two Pif1 family DNA helicases, Pif1 and Rrm3. Rrm3 promotes DNA replication past stable protein complexes at tRNA genes (tDNAs). We identify a new role for the Pif1 helicase: promotion of replication and suppression of DNA damage at tDNAs. Pif1 binds multiple tDNAs, and this binding is higher in rrm3Δ cells. Accumulation of replication intermediates and DNA damage at tDNAs is higher in pif1Δ rrm3Δ than in rrm3Δ cells. DNA damage at tDNAs in the absence of these helicases is suppressed by destabilizing R-loops while Pif1 and Rrm3 binding to tDNAs is increased upon R-loop stabilization. We propose that Rrm3 and Pif1 promote genome stability at tDNAs by displacing the stable multi-protein transcription complex and by removing R-loops. Thus, we identify tDNAs as a new source of R-loop-mediated DNA damage. Given their large number and high transcription rate, tDNAs may be a potent source of genome instability. The budding yeast genome encodes two Pif1 family helicases, Pif1 and Rrm3, previously shown to have distinct functions in the maintenance of telomeres and other aspects of genome stability. Here the authors identify a role for Pif1 (and Rrm3) in promoting DNA replication and suppressing R-loop mediated DNA damage at tRNA genes.