title: Replication factory activation can be decoupled from the replication timing program by modulating Cdk levels.
abstract: In the metazoan replication timing program, clusters of replication origins located in different subchromosomal domains fire at different times during S phase. We have used Xenopus laevis egg extracts to drive an accelerated replication timing program in mammalian nuclei. Although replicative stress caused checkpoint-induced slowing of the timing program, inhibition of checkpoint kinases in an unperturbed S phase did not accelerate it. Lowering cyclin-dependent kinase (Cdk) activity slowed both replication rate and progression through the timing program, whereas raising Cdk activity increased them. Surprisingly, modest alteration of Cdk activity changed the amount of DNA synthesized during different stages of the timing program. This was associated with a change in the number of active replication factories, whereas the distribution of origins within active factories remained relatively normal. The ability of Cdks to differentially effect replication initiation, factory activation, and progression through the timing program provides new insights into the way that chromosomal DNA replication is organized during S phase.
authors.affiliation: Wellcome Trust Centre for Gene Regulation and Expression, College of Life Sciences, University of Dundee, Dundee DD1 5EH, Scotland, UK.
authors.forename: Alexander M
authors.initials: AM
authors.lastname: Thomson
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Gillespie
authors.forename: J Julian
authors.initials: JJ
authors.lastname: Blow
mesh_terms: D000818:Animals; D016203:CDC2 Protein Kinase / Q000235:genetics* / Q000378:metabolism*; D016466:CHO Cells; D002453:Cell Cycle / Q000235:genetics; D006224:Cricetinae; D003412:Cricetulus; D004247:DNA / Q000096:biosynthesis; D004261:DNA Replication / Q000235:genetics*; D004789:Enzyme Activation / Q000235:genetics; D018816:Genes, cdc / Q000502:physiology*; D008938:Mitosis / Q000235:genetics*; D016196:S Phase / Q000235:genetics; D013312:Stress, Physiological / Q000235:genetics; D013997:Time Factors; D014982:Xenopus laevis
chemical_list: D004247:DNA; D016203:CDC2 Protein Kinase