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Biol Open. 2016 Oct 15;5(10):1449-1460. doi: 10.1242/bio.019729.

Regulation of DNA replication and chromosomal polyploidy by the MLL-WDR5-RBBP5 methyltransferases.

Author information

1
Laboratory of Chemical Genomics, School of Chemical Biology and Biotechnology, Peking University Shenzhen Graduate School, Shenzhen, Guangdong 518055, China Basic Science Division, Nevada Cancer Institute, Las Vegas, NV 89135, USA.
2
Laboratory of Chemical Genomics, School of Chemical Biology and Biotechnology, Peking University Shenzhen Graduate School, Shenzhen, Guangdong 518055, China.
3
Basic Science Division, Nevada Cancer Institute, Las Vegas, NV 89135, USA.
4
Department of Chemistry and Biochemistry, University of Nevada, Las Vegas, NV 89154, USA.
5
Basic Science Division, Nevada Cancer Institute, Las Vegas, NV 89135, USA Department of Chemistry and Biochemistry, University of Nevada, Las Vegas, NV 89154, USA.
6
Basic Science Division, Nevada Cancer Institute, Las Vegas, NV 89135, USA Department of Chemistry and Biochemistry, University of Nevada, Las Vegas, NV 89154, USA hui.zhang@unlv.edu.

Abstract

DNA replication licensing occurs on chromatin, but how the chromatin template is regulated for replication remains mostly unclear. Here, we have analyzed the requirement of histone methyltransferases for a specific type of replication: the DNA re-replication induced by the downregulation of either Geminin, an inhibitor of replication licensing protein CDT1, or the CRL4CDT2 ubiquitin E3 ligase. We found that siRNA-mediated reduction of essential components of the MLL-WDR5-RBBP5 methyltransferase complexes including WDR5 or RBBP5, which transfer methyl groups to histone H3 at K4 (H3K4), suppressed DNA re-replication and chromosomal polyploidy. Reduction of WDR5/RBBP5 also prevented the activation of H2AX checkpoint caused by re-replication, but not by ultraviolet or X-ray irradiation; and the components of MLL complexes co-localized with the origin recognition complex (ORC) and MCM2-7 replicative helicase complexes at replication origins to control the levels of methylated H3K4. Downregulation of WDR5 or RBBP5 reduced the methylated H3K4 and suppressed the recruitment of MCM2-7 complexes onto replication origins. Our studies indicate that the MLL complexes and H3K4 methylation are required for DNA replication but not for DNA damage repair.

KEYWORDS:

DNA replication; H3K4 methylation; RBBP5; Re-replication; WDR5

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