Читать книгу Snyder and Champness Molecular Genetics of Bacteria - Tina M. Henkin - Страница 106

In addition to the GATC/CTAG sequences associated with oriC and the dnaA promoter, SeqA also interacts with the GATC/CTAG sequences as the replication forks progress around the chromosome, effectively marking the location of the replisome (Figure 1.25). SeqA bound to transiently hemimethylated GATC/CTAG sites immediately behind the DNA replication forks may be capable of bringing together the nascent sister chromosomes, and it also appears to negatively regulate the decatenation activity of topoisomerase (see Joshi et al., Suggested Reading). Both of these processes may mediate a form of sister chromosome cohesion that in turn may help to regulate processing of the new DNAs by positioning them for DNA repair and recombination. Interestingly, SeqA is essential in mutants that lack the major pathways of DNA recombination involving RecA, supporting an additional role in protecting genome integrity. Additionally, chromosomes appear to be vulnerable to many types of mobile DNA elements during DNA replication, especially when replication forks stall (see Fricker and Peters, Suggested Reading). SeqA-facilitated processes may help to protect DNA replication forks from mobile elements as one of multiple mechanisms of protecting genome integrity.