Prado Félix, Aguilera Andrés
Departamento de Genética, Facultad de Biología, Universidad de Sevilla, Sevilla, Spain.
EMBO J. 2005 Mar 23;24(6):1267-76. doi: 10.1038/sj.emboj.7600602. Epub 2005 Mar 3.
Homologous recombination safeguards genome integrity, but it can also cause genome instability of important consequences for cell proliferation and organism development. Transcription induces recombination, as shown in prokaryotes and eukaryotes for both spontaneous and developmentally regulated events such as those responsible for immunoglobulin class switching. Deciphering the molecular basis of transcription-associated recombination (TAR) is important in understanding genome instability. Using novel plasmid-borne recombination constructs in Saccharomyces cerevisiae, we show that RNA polymerase II (RNAPII) transcription induces recombination by impairing replication fork progression. RNAPII transcription concomitant to head-on oncoming replication causes a replication fork pause (RFP) that is linked to a significant increase in recombination. However, transcription that is codirectional with replication has little effect on replication fork progression and recombination. Transcription occurring in the absence of replication does not affect either recombination or replication fork progression. The Rrm3 helicase, which is required for replication fork progression through nucleoprotein complexes, facilitates replication through the transcription-dependent RFP site and reduces recombination. Therefore, our work provides evidence that one mechanism responsible for TAR is RNAP-mediated replication impairment.
同源重组保障基因组完整性，但它也可能导致基因组不稳定，对细胞增殖和生物体发育产生重要影响。转录会诱导重组，这在原核生物和真核生物中均有体现，无论是自发的还是发育调控的事件，如负责免疫球蛋白类别转换的事件。解读转录相关重组（TAR）的分子基础对于理解基因组不稳定至关重要。利用酿酒酵母中新型的质粒携带重组构建体，我们发现RNA聚合酶II（RNAPII）转录通过损害复制叉进展来诱导重组。与迎面而来的复制同时发生的RNAPII转录会导致复制叉停顿（RFP），这与重组的显著增加相关。然而，与复制同向的转录对复制叉进展和重组影响很小。在没有复制的情况下发生的转录既不影响重组也不影响复制叉进展。Rrm3解旋酶是复制叉通过核蛋白复合物所必需的，它促进通过转录依赖性RFP位点的复制并减少重组。因此，我们的工作提供了证据，表明TAR的一种机制是RNAP介导的复制损伤。
