Publication Date:
2010-09-08
Description:
Cell cycle checkpoints are implemented to safeguard the genome, avoiding the accumulation of genetic errors. Checkpoint loss results in genomic instability and contributes to the evolution of cancer. Among G1-, S-, G2- and M-phase checkpoints, genetic studies indicate the role of an intact S-phase checkpoint in maintaining genome integrity. Although the basic framework of the S-phase checkpoint in multicellular organisms has been outlined, the mechanistic details remain to be elucidated. Human chromosome-11 band-q23 translocations disrupting the MLL gene lead to poor prognostic leukaemias. Here we assign MLL as a novel effector in the mammalian S-phase checkpoint network and identify checkpoint dysfunction as an underlying mechanism of MLL leukaemias. MLL is phosphorylated at serine 516 by ATR in response to genotoxic stress in the S phase, which disrupts its interaction with, and hence its degradation by, the SCF(Skp2) E3 ligase, leading to its accumulation. Stabilized MLL protein accumulates on chromatin, methylates histone H3 lysine 4 at late replication origins and inhibits the loading of CDC45 to delay DNA replication. Cells deficient in MLL showed radioresistant DNA synthesis and chromatid-type genomic abnormalities, indicative of S-phase checkpoint dysfunction. Reconstitution of Mll(-/-) (Mll also known as Mll1) mouse embryonic fibroblasts with wild-type but not S516A or DeltaSET mutant MLL rescues the S-phase checkpoint defects. Moreover, murine myeloid progenitor cells carrying an Mll-CBP knock-in allele that mimics human t(11;16) leukaemia show a severe radioresistant DNA synthesis phenotype. MLL fusions function as dominant negative mutants that abrogate the ATR-mediated phosphorylation/stabilization of wild-type MLL on damage to DNA, and thus compromise the S-phase checkpoint. Together, our results identify MLL as a key constituent of the mammalian DNA damage response pathway and show that deregulation of the S-phase checkpoint incurred by MLL translocations probably contributes to the pathogenesis of human MLL leukaemias.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2940944/" target="_blank"〉〈img src="https://static.pubmed.gov/portal/portal3rc.fcgi/4089621/img/3977009" border="0"〉〈/a〉 〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2940944/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Liu, Han -- Takeda, Shugaku -- Kumar, Rakesh -- Westergard, Todd D -- Brown, Eric J -- Pandita, Tej K -- Cheng, Emily H-Y -- Hsieh, James J-D -- CA119008/CA/NCI NIH HHS/ -- CA123232/CA/NCI NIH HHS/ -- CA129537/CA/NCI NIH HHS/ -- R01 CA119008/CA/NCI NIH HHS/ -- R01 CA119008-01/CA/NCI NIH HHS/ -- R01 CA119008-02/CA/NCI NIH HHS/ -- R01 CA119008-03/CA/NCI NIH HHS/ -- R01 CA119008-04/CA/NCI NIH HHS/ -- R01 CA119008-05/CA/NCI NIH HHS/ -- England -- Nature. 2010 Sep 16;467(7313):343-6. doi: 10.1038/nature09350. Epub 2010 Sep 5.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Medicine, Washington University School of Medicine, St Louis, Missouri 63110, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/20818375" target="_blank"〉PubMed〈/a〉
Keywords:
Alleles
;
Animals
;
Ataxia Telangiectasia Mutated Proteins
;
Cell Cycle Proteins/*metabolism
;
Cell Line
;
Chromatin/metabolism
;
DNA Damage
;
DNA Replication/physiology
;
Genes, Dominant/genetics
;
Genomic Instability/physiology
;
Histone-Lysine N-Methyltransferase
;
Histones/chemistry/metabolism
;
Humans
;
Leukemia/genetics
;
Lysine/metabolism
;
Methylation
;
Mice
;
Myeloid Progenitor Cells/metabolism
;
Myeloid-Lymphoid Leukemia Protein/chemistry/deficiency/genetics/*metabolism
;
Phosphorylation
;
Phosphoserine/metabolism
;
Protein Binding
;
Protein-Serine-Threonine Kinases/*metabolism
;
S Phase/*physiology
;
S-Phase Kinase-Associated Proteins/metabolism
;
Signal Transduction
;
Translocation, Genetic/genetics
Print ISSN:
0028-0836
Electronic ISSN:
1476-4687
Topics:
Biology
,
Chemistry and Pharmacology
,
Medicine
,
Natural Sciences in General
,
Physics
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