Are multiple checkpoint mediators involved in a checkpoint linking histone gene expression with DNA replication?

In metazoans, accurate replication of chromosomes is ensured by the coupling of DNA synthesis to the synthesis of histone proteins. Expression of replication-dependent histone genes is restricted to S-phase by a combination of cell cycle-regulated transcriptional and post-transcriptional control mechanisms and is linked to DNA replication by a poorly understood mechanism involving checkpoint kinases [Su, Gao, Schneider, Helt, Weiss, O'Reilly, Bohmann and Zhao (2004) EMBO J. 23, 1133-1143; Kaygun and Marzluff (2005) Nat. Struct. Mol. Biol. 12, 794-800]. Here we propose a model for the molecular mechanisms that link these two important processes within S-phase, and propose roles for multiple checkpoints in this mechanism.