title: 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 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.
authors.affiliation: Department of Pathology, University of Michigan, Ann Arbor, Michigan 48109, USA.
authors.forename: Shan
authors.initials: S
authors.lastname: Gao
authors.forename: Jie
authors.initials: J
authors.lastname: Xiong
authors.forename: Chunchao
authors.initials: C
authors.lastname: Zhang
authors.forename: Brian R
authors.initials: BR
authors.lastname: Berquist
authors.forename: Rendong
authors.initials: R
authors.lastname: Yang
authors.forename: Meng
authors.initials: M
authors.lastname: Zhao
authors.forename: Anthony J
authors.initials: AJ
authors.lastname: Molascon
authors.forename: Shaina Y
authors.initials: SY
authors.lastname: Kwiatkowski
authors.forename: Dongxia
authors.initials: D
authors.lastname: Yuan
authors.forename: Zhaohui
authors.initials: Z
authors.lastname: Qin
authors.forename: Jianfan
authors.initials: J
authors.lastname: Wen
authors.forename: Geoffrey M
authors.initials: GM
authors.lastname: Kapler
authors.forename: Philip C
authors.initials: PC
authors.lastname: Andrews
authors.forename: Wei
authors.initials: W
authors.lastname: Miao
authors.forename: Yifan
authors.initials: Y
authors.lastname: Liu
mesh_terms: D004261:DNA Replication / Q000235:genetics*; D004277:DNA, Single-Stranded / Q000378:metabolism; D006657:Histones / Q000235:genetics / Q000378:metabolism*; D008745:Methylation; D009154:Mutation; D018809:Proliferating Cell Nuclear Antigen / Q000378:metabolism; D012097:Repressor Proteins / Q000378:metabolism; D016808:Tetrahymena thermophila / Q000235:genetics* / Q000378:metabolism*
chemical_list: D004277:DNA, Single-Stranded; D006657:Histones; D018809:Proliferating Cell Nuclear Antigen; D012097:Repressor Proteins
keywords: H3 Lys 27 methylation; histone methyltransferase; replication elongation; replication origin; replication stress; ssDNA