Histone H3 Thr 45 phosphorylation is a replication-associated post-translational modification in S. cerevisiae

Department of Biochemistry and Molecular Genetics, University of Virginia School of Medicine, Charlottesville, VA 22908, USA.
Nature Cell Biology (Impact Factor: 19.68). 02/2010; 12(3):294-8. DOI: 10.1038/ncb2030
Source: PubMed


Post-translational histone modifications are crucial for the regulation of numerous DNA-templated processes, and are thought to mediate both alteration of chromatin dynamics and recruitment of effector proteins to specific regions of the genome. In particular, histone Ser/Thr phosphorylation regulates multiple nuclear functions in the budding yeast Saccharomyces cerevisiae, including transcription, DNA damage repair, mitosis, apoptosis and sporulation. Although modifications to chromatin during replication remain poorly understood, a number of recent studies have described acetylation of the histone H3 N-terminal alpha-helix (alphaN helix) at Lys 56 as a modification that is important for maintenance of genomic integrity during DNA replication and repair. Here, we report phosphorylation of H3 Thr 45 (H3-T45), a histone modification also located within the H3 alphaN helix in S. cerevisiae. Thr 45 phosphorylation peaks during DNA replication, and is mediated by the S phase kinase Cdc7-Dbf4 as part of a multiprotein complex identified in this study. Furthermore, loss of phosphorylated H3-T45 causes phenotypes consistent with replicative defects, and prolonged replication stress results in H3-T45 phosphorylation accumulation over time. Notably, the phenotypes described here are independent of Lys 56 acetylation status, and combinatorial mutations to both Thr 45 and Lys 56 of H3 cause synthetic growth defects. Together, these data identify and characterize H3-T45 phosphorylation as a replication-associated histone modification in budding yeast.

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    • "It is important to note that Thr45 is located within the histone fold domain (Fig. S1). The phosphorylation of this site was described recently by three groups [Hurd et al., 2009; Baker et al., 2010; Villagrasa et al., 2012]. Having established that recombinant S6K2 has a much higher affinity towards histone H3 than its relative kinase homologue S6K1 in vitro, we then investigated if the phosphorylation site in H3 recognised by S6K2 in vitro is Thr45. "
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