Veaute Xavier, Delmas Stéphane, Selva Marjorie, Jeusset Josette, Le Cam Eric, Matic Ivan, Fabre Francis, Petit Marie-Agnès
CEA, DSV, DRR, UMR217 CNRS/CEA, Fontenay aux roses, France.
EMBO J. 2005 Jan 12;24(1):180-9. doi: 10.1038/sj.emboj.7600485. Epub 2004 Nov 25.
The roles of UvrD and Rep DNA helicases of Escherichia coli are not yet fully understood. In particular, the reason for rep uvrD double mutant lethality remains obscure. We reported earlier that mutations in recF, recO or recR genes suppress the lethality of uvrD rep, and proposed that an essential activity common to UvrD and Rep is either to participate in the removal of toxic recombination intermediates or to favour the proper progression of replication. Here, we show that UvrD, but not Rep, directly prevents homologous recombination in vivo. In addition to RecFOR, we provide evidence that RecA contributes to toxicity in the rep uvrD mutant. In vitro, UvrD dismantles the RecA nucleoprotein filament, while Rep has only a marginal activity. We conclude that UvrD and Rep do not share a common activity that is essential in vivo: while Rep appears to act at the replication stage, UvrD plays a role of RecA nucleoprotein filament remover. This activity of UvrD is similar to that of the yeast Srs2 helicase.
大肠杆菌中UvrD和Rep DNA解旋酶的作用尚未完全明确。特别是，rep uvrD双突变致死的原因仍不清楚。我们之前报道过，recF、recO或recR基因中的突变可抑制uvrD rep的致死性，并提出UvrD和Rep共有的一种基本活性要么是参与清除有毒的重组中间体，要么是促进复制的正常进行。在这里，我们表明UvrD而非Rep在体内直接阻止同源重组。除了RecFOR，我们还提供证据表明RecA也导致rep uvrD突变体中的毒性。在体外，UvrD可拆解RecA核蛋白丝，而Rep只有微弱的活性。我们得出结论，UvrD和Rep在体内并不具有共同的必需活性：Rep似乎在复制阶段起作用，而UvrD则发挥RecA核蛋白丝清除剂的作用。UvrD的这种活性与酵母Srs2解旋酶的活性相似。
