Impaired replication elongation in Tetrahymena mutants deficient in histone H3 Lys 27 monomethylation
- Shan Gao1,10,
- Jie Xiong2,3,10,
- Chunchao Zhang4,
- Brian R. Berquist5,
- Rendong Yang6,
- Meng Zhao6,
- Anthony J. Molascon1,
- Shaina Y. Kwiatkowski1,
- Dongxia Yuan2,
- Zhaohui Qin6,7,
- Jianfan Wen3,
- Geoffrey M. Kapler5,
- Philip C. Andrews4,8,9,
- Wei Miao2,11 and
- Yifan Liu1,11
- 1Department of Pathology, University of Michigan, Ann Arbor, Michigan 48109, USA;
- 2Key Laboratory of Aquatic Biodiversity and Conservation, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China;
- 3State Key Laboratory of Genetic Resources and Evolution, Kunming Institute of Zoology, Chinese Academy of Sciences, China;
- 4Department of Computational Medicine and Bioinformatics, University of Michigan, Ann Arbor, Michigan 48109, USA;
- 5Department of Molecular and Cellular Medicine, College of Medicine, Texas A&M Health Science Center, College Station, Texas 77843, USA;
- 6Department of Biostatistics and Bioinformatics, Emory University, Atlanta, Georgia 30322, USA;
- 7Center for Comprehensive Informatics, Emory University, Atlanta, Georgia 30322, USA;
- 8Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, USA
- 9Department of Biological Chemistry, University of Michigan, Ann Arbor, Michigan 48109, USA
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↵10 These authors contributed equally to this work.
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 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.
Keywords
- histone methyltransferase
- H3 Lys 27 methylation
- replication stress
- replication elongation
- ssDNA
- replication origin
Footnotes
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↵11 Corresponding authors
E-mail yifan{at}med.umich.edu
E-mail miaowei{at}ihb.ac.cn
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Supplemental material is available for this article.
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Article published online ahead of print. Article and publication date are online at http://www.genesdev.org/cgi/doi/10.1101/gad.218966.113.
- Received April 2, 2013.
- Accepted July 1, 2013.
- Copyright © 2013 by Cold Spring Harbor Laboratory Press
