Book of Abstracts: Albany 2011
June 14-18 2011
©Adenine Press (2010)
The E. coli Replisome and Use of Clamps to Bypass Replication Barriers
Chromosomal replicases utilize circular sliding clamps for high-processivity during replication. Sliding clamps not only bind the chromosomal replicase, but they also function with all 5 DNA polymerases in E. coli as well as other proteins for repair and lesion bypass. This presentation focuses on the use of the sliding clamp by the replicase in crossing barriers that are encountered during replication. Studies have shown that the replicase, Pol III, can rapidly hop from one sliding clamp to another clamp in order to transfer to the multiple RNA primers synthesized during lagging strand replication. However, recent studies indicate that polymerase hopping among sliding clamps is of more general use, and can allow the polymerase to bypass lesions and even to circumvent a tightly bound RNA polymerase that it encounters during replication. We will present studies that demonstrate the how the replisome deals with collisions with RNA polymerase transcribing either the leading or lagging strand template. We will also present our findings on how different polymerases control the use of the clamp to form alternative replisomes for DNA damage avoidance and, when needed, to deal with lesions that are encountered directly. Finally, we present single-molecule studies that examine replisome action during lagging strand synthesis and the consequences for the leading strand polymerase.
Roxana E. Georgescu