Evidence for two different regulatory mechanisms linking replication and segregation of vibrio cholerae chromosome II.

Tatiana Venkova-Canova, Jong Hwan Baek, Peter C Fitzgerald, Melanie Blokesch, Dhruba K Chattoraj

PLoS genetics 2013 Jun

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Understanding the mechanisms that coordinate replication initiation with subsequent segregation of chromosomes is an important biological problem. Here we report two replication-control mechanisms mediated by a chromosome segregation protein, ParB2, encoded by chromosome II of the model multichromosome bacterium, Vibrio cholerae. We find by the ChIP-chip assay that ParB2, a centromere binding protein, spreads beyond the centromere and covers a replication inhibitory site (a 39-mer). Unexpectedly, without nucleation at the centromere, ParB2 could also bind directly to a related 39-mer. The 39-mers are the strongest inhibitors of chromosome II replication and they mediate inhibition by binding the replication initiator protein. ParB2 thus appears to promote replication by out-competing initiator binding to the 39-mers using two mechanisms: spreading into one and direct binding to the other. We suggest that both these are novel mechanisms to coordinate replication initiation with segregation of chromosomes.

Citation

Tatiana Venkova-Canova, Jong Hwan Baek, Peter C Fitzgerald, Melanie Blokesch, Dhruba K Chattoraj. Evidence for two different regulatory mechanisms linking replication and segregation of vibrio cholerae chromosome II. PLoS genetics. 2013 Jun;9(6):e1003579