Impaired replication elongation in Tetrahymena mutants deficient in histone H3 Lys 27 monomethylation.

ABSTRACT: Replication of nuclear DNA occurs in the context of chromatin and is influenced by histone modifications. In the ciliate Tetrahymena thermophila, we identified TXR1, encoding a histone methyltransferase. TXR1 deletion resulted in severe DNA replication stress, manifested by the accumulation of ssDNA, production of aberrant replication intermediates, and activation of robust DNA damage responses. Paired-end Illumina sequencing of ssDNA revealed intergenic regions, including replication origins, as hot spots for replication stress in ?TXR1 cells. ?TXR1 cells showed a deficiency in histone H3 Lys 27 monomethylation (H3K27me1), while ?EZL2 cells, deleting a Drosophila E(z) homolog, were deficient in H3K27 di- and trimethylation, with no detectable replication stress. A point mutation in histone H3 at Lys 27 (H3 K27Q) mirrored the phenotype of ?TXR1, corroborating H3K27me1 as a key player in DNA replication. Additionally, we demonstrated interactions between TXR1 and proliferating cell nuclear antigen (PCNA). These findings support a conserved pathway through which H3K27me1 facilitates replication elongation.

SUBMITTER: Gao S 

PROVIDER: S-EPMC3744725 | biostudies-literature | 2013 Aug

REPOSITORIES: biostudies-literature