Segregation of replicative dna polymerases during s phase

Abstract

DNA polymerases (Pol) alpha, delta, and is an element of replicate the bulk of chromosomal DNA in eukaryotic cells, Pol is an element of being the main leading strand and Pol delta the lagging strand DNA polymerase. By applying chromatin immunoprecipitation (ChIP) and quantitative PCR we found that at G(1)/S arrest, all three DNA polymerases were enriched with DNA containing the early firing lamin B2 origin of replication and, 2 h after release from the block, with DNA containing the origin at the upstream promoter region of the MCM4 gene. Pol alpha, delta, and is an element of were released from these origins upon firing. All three DNA polymerases, Mcm3 and Cdc45, but not Orc2, still formed complexes in late S phase. Reciprocal ChIP of the three DNA polymerases revealed that at G(1)/S arrest and early in S phase, Pol alpha, delta, and is an element of were associated with the same nucleoprotein complexes, whereas in late S phase Pol is an element of and Pol alpha/delta were largely associated with distinct complexes. At G(1)/S arrest, the replicative DNA polymerases were associated with lamins, but in late S phase only Pol is an element of, not Pol alpha/delta, remained associated with lamins. Consistently, Pol is an element of, but not Pol delta, was found in nuclear matrix fraction throughout the cell cycle. Therefore, Pol is an element of and Pol alpha/delta seem to pursue their functions at least in part independently in late S phase, either by physical uncoupling of lagging strand maturation from the fork progression, or by recruitment of Pol delta, but not Pol is an element of, to post-replicative processes such as translesion synthesis or post-replicative repair.