Liu J, Xu L, Sandler S J, Marians K J
Molecular Biology Graduate Program, Cornell University Graduate School of Medical Sciences, New York, NY 10021, USA.
Proc Natl Acad Sci U S A. 1999 Mar 30;96(7):3552-5. doi: 10.1073/pnas.96.7.3552.
PriA, a 3' --> 5' DNA helicase, directs assembly of a primosome on some bacteriophage and plasmid DNAs. Primosomes are multienzyme replication machines that contribute both the DNA-unwinding and Okazaki fragment-priming functions at the replication fork. The role of PriA in chromosomal replication is unclear. The phenotypes of priA null mutations suggest that the protein participates in replication restart at recombination intermediates. We show here that PriA promotes replication fork assembly at a D loop, an intermediate formed during initiation of homologous recombination. We also show that DnaC810, encoded by a naturally arising intergenic suppressor allele of the priA2::kan mutation, bypasses the need for PriA during replication fork assembly at D loops in vitro. These findings underscore the essentiality of replication fork restart at recombination intermediates under normal growth conditions in bacteria.
PriA是一种3'→5' DNA解旋酶，可指导在某些噬菌体和质粒DNA上组装引发体。引发体是多酶复制机器，在复制叉处发挥DNA解旋和冈崎片段引发功能。PriA在染色体复制中的作用尚不清楚。priA缺失突变的表型表明该蛋白参与重组中间体处的复制重启。我们在此表明，PriA促进D环处的复制叉组装，D环是同源重组起始过程中形成的中间体。我们还表明，priA2::kan突变的天然发生的基因间抑制等位基因编码的DnaC810在体外D环处的复制叉组装过程中绕过了对PriA的需求。这些发现强调了在细菌正常生长条件下重组中间体处复制叉重启的必要性。
