Coordination of DNA replication and histone modification by the Rik1–Dos2 complex

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Histone modification marks have an important role in many chromatin processes1,2. During DNA replication, both heterochromatin and euchromatin are disrupted ahead of the replication fork and are then reassembled into their original epigenetic states behind the fork3,4. How histone marks are accurately inherited from generation to generation is still poorly understood. In fission yeast (Schizosaccharomyces pombe), RNA interference (RNAi)-mediated histone methylation is cell cycle regulated. Centromeric repeats are transiently transcribed in the S phase of the cell cycle and are processed into short interfering RNAs (siRNAs) by the complexes RITS (RNA-induced initiation of transcriptional gene silencing) and RDRC (RNA-directed RNA polymerase complex)5,6,7. The small RNAs together with silencing factors—including Dos1 (also known as Clr8 and Raf1), Dos2 (also known as Clr7 and Raf2), Rik1 and Lid2—promote heterochromatic methylation of histone H3 at lysine 9 (H3K9) by a histone methyltransferase, Clr4 (refs 8–13). The methylation of H3K9 provides a binding site for Swi6, a structural and functional homologue of metazoan heterochromatin protein 1 (HP1)14. Here we characterize a silencing complex in fission yeast that contains Dos2, Rik1, Mms19 and Cdc20 (the catalytic subunit of DNA polymerase-ε). This complex regulates RNA polymerase II (RNA Pol II) activity in heterochromatin and is required for DNA replication and heterochromatin assembly. Our findings provide a molecular link between DNA replication and histone methylation, shedding light on how epigenetic marks are transmitted during each cell cycle.

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Figure 1: Cdc20 is essential for transcriptional silencing and siRNA generation.
Figure 2: Heterochromatin abnormality is coupled to DNA replication defects.
Figure 3: Mms19 is required for RNA-Pol-II-mediated transcription of heterochromatin.
Figure 4: Functional interactions between components of the Dos2-containing complex.


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We thank R. Allshire, P. Nurse, G. D’Urso and the Japan Yeast Genetic Resource Center for strains, E. Osborne and C. Hale for comments on the manuscript, Cold Spring Harbor Laboratory for mass spectrometry analysis, and members of the Cande and Li laboratories for their support and discussions. This work was supported by a grant from the National Institutes of Health (RO1GM076396) to W.Z.C. and R.M.

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F.L. and W.Z.C. designed the experiments and wrote the manuscript. F.L. performed the experiments. R.M. provided mass spectrometry expertise, equipment and conceptual support.

Correspondence to Fei Li.

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Li, F., Martienssen, R. & Cande, W. Coordination of DNA replication and histone modification by the Rik1–Dos2 complex. Nature 475, 244–248 (2011) doi:10.1038/nature10161

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