Article

The Histone H4 Lysine 20 Monomethyl Mark, Set by PR-Set7 and Stabilized by L(3)mbt, Is Necessary for Proper Interphase Chromatin Organization

Ludwig-Maximilians-Universität München, Germany
PLoS ONE (Impact Factor: 3.53). 09/2012; 7(9):e45321. DOI: 10.1371/journal.pone.0045321
Source: PubMed

ABSTRACT Drosophila PR-Set7 or SET8 is a histone methyltransferase that specifically monomethylates histone H4 lysine 20 (H4K20). L(3)MBT has been identified as a reader of methylated H4K20. It contains several conserved domains including three MBT repeats binding mono- and dimethylated H4K20 peptides. We find that the depletion of PR-Set7 blocks de novo H4K20me1 resulting in the immediate activation of the DNA damage checkpoint, an increase in the size of interphase nuclei, and drastic reduction of cell viability. L(3)mbt on the other hand stabilizes the monomethyl mark, as L(3)mbt-depleted S2 cells show a reduction of more than 60% of bulk monomethylated H4K20 (H4K20me1) while viability is barely affected. Ploidy and basic chromatin structure show only small changes in PR-Set7-depleted cells, but higher order interphase chromatin organization is significantly affected presumably resulting in the activation of the DNA damage checkpoint. In the absence of any other known functions of PR-Set7, the setting of the de novo monomethyl mark appears essential for cell viability in the presence or absence of the DNA damage checkpoint, but once newly assembled chromatin is established the monomethyl mark, protected by L(3)mbt, is dispensable.

0 Followers
 · 
114 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: H4K20me1 is a critical histone lysine methyl modification in eukaryotes. It is recognized and "read" by various histone lysine methyl modification binding proteins. In this study, the function of MBTD1, a member of the Polycomb protein family containing four MBT domains, was comprehensively studied in mouse oocyte meiotic maturation. The results showed that depletion of MBTD1 caused reduced expression of histone lysine methyl transferase Pr-Set7 and H4K20me1 as well as increased oocyte arrest at the GV stage. Increased γH2AX foci were formed, and DNA damage repair checkpoint protein 53BP1 was downregulated. Furthermore, depletion of MBTD1 activated the cell cycle checkpoint protein chk1 and downregulated the expression of cyclin B1 and cdc2. MBTD1 knockdown also affected chromosome configuration in GV stage oocytes and chromosome alignment at the MII stage. All these phenotypes were reproduced when the H4k20 methyl transferase Pr-Set7 was depleted. Co-IP demonstrated that MBTD1 was correlated with Pr-Set7 in mouse oocytes. Our results demonstrate that MBTD1 is associated with Pr-Set7 to stabilize H4K20me1 in mouse oocyte meiotic maturation.
    Cell cycle (Georgetown, Tex.) 03/2013; 12(7). DOI:10.4161/cc.24216 · 5.01 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: In human cells appropriate mono-methylation of histone H4 lysine20 by PrSet7/SET8 is important for the correct transcription of specific genes, and timely progression through the cell cycle. Over-methylation appears to be prevented through the interaction of PrSet7 with PCNA, which targets PrSet7 destruction via the CRL4(cdt2) pathway, however the factors involved in positive regulation of its histone methylation remain undefined.Here we present biochemical and genetic evidence for a previously undocumented interaction between dPrSet7 and DNA polymerase-alpha in Drosophila. Depletion of the polymerase reduces H4K20 mono-methylation suggesting that it is required for the expression of dPrSet7 histone methylation activity. We also show that the interaction between PCNA and PrSet7 is conserved in Drosophila, but is only detectable in chromatin fractions. Consistent with this, S2 cells show a significant loss of chromatin bound dPrSet7 protein as S phase progresses.Based on these data we suggest that interaction with the DNA polymerase represents an important route for the expression of PrSet7 histone methylase activity, by allowing loading of dPrSet7 onto chromatin or its subsequent activation.
    Journal of Cell Science 05/2014; 127(14). DOI:10.1242/jcs.144501 · 5.33 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Lethal malignant brain tumors (lmbt) result from the loss of the conserved transcriptional repressor l(3)mbt, in Drosophila melanogaster. Similar mutations in the human homolog L3MBTL1 correlate with some cancers. The protein's C-terminal MBT repeats bind mono and dimethylated histones in vitro, which could influence recruitment of L3MBTL1 to its target sites. The L(3)mbt chromatin targeting mechanism, however, is controversial and several studies suggest insufficiency or a minor role for histone methylation in determining the site specificity for recruitment. We report that L(3)mbt colocalizes with core members of the Myb-MuvB/DREAM (MMB/DREAM) transcriptional regulatory complex genome-wide, and that L(3)mbt-mediated repression requires this complex in salivary glands and larval brains. Loss of l(3)mbt or of MMB components through mutation cause similar spurious expression of genes, including the transposon regulatory gene piwi, in terminally differentiated cells. The DNA-binding MMB core component Mip120 (Lin54) is required for L(3)mbt recruitment to chromosomes, whereas Mip130 (Lin9) (an MMB core protein) and E2f2 (an MMB transcriptional repressor) are not, but are essential for repression. Cytolocalization experiments suggest the presence of site-specific differential composition of MMB in polytene chromosomes where some loci were bound by a Myb-containing or alternatively, an E2f2 and L(3)mbt form of the complex.
    Proceedings of the National Academy of Sciences 09/2014; 111(40). DOI:10.1073/pnas.1416321111 · 9.81 Impact Factor

Preview (2 Sources)

Download
0 Downloads
Available from