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

Shan Gao, Jie Xiong, Chunchao Zhang, Brian R. Berquist, Rendong Yang, Meng Zhao, Anthony J. Molascon, Shaina Y. Kwiatkowski, Dongxia Yuan, Zhaohui Qin, Jianfan Wen, Geoffrey M. Kapler, Philip C. Andrews, Wei Miao, Yifan Liu

Research output: Contribution to journalArticlepeer-review

46 Scopus citations


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 ΔTXR1 cells. ΔTXR1 cells showed a deficiency in histone H3 Lys 27 monomethylation (H3K27me1), while ΔEZL2 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 ΔTXR1, 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.

Original languageEnglish (US)
Pages (from-to)1662-1679
Number of pages18
JournalGenes and Development
Issue number15
StatePublished - Aug 1 2013
Externally publishedYes


  • H3 Lys 27 methylation
  • Histone methyltransferase
  • Replication elongation
  • Replication origin
  • Replication stress
  • ssDNA


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