| Structural highlights
Function
[MOM1_ARATH] Required for the heritable maintenance of transcriptional gene silencing (TGS) in heterochromatin, and particularly in the intermediate bivalent heterochromatin, characterized by an unsual methylation pattern consisting in hypermethylated DNA and histone H3 'Lys-4' methylation (H3K4me) together with depletion of histone H3 'Lys-9' methylation (H3K9me), in a chromatin methylation-independent manner, in a non-CG methylation context. May play a role in the RNA polymerase IV/V (Pol-IV/V)-mediated RNA-directed DNA methylation (RdDM) leading to TGS (also called siRNA-mediated TGS pathway), probably by modulating small interfering RNA (siRNA) accumulation. Especially involved in the gene silencing of the transcriptionally silent information region (TSI), 5S ribosomal RNA genes (localized in the pericentromeric heterochromatin of chromosomes 3, 4, and 5) and of 180-bp satellite repeats and 106B long terminal repeat (LTR)-like repeats of the chromocenters. Prevents the aberrant mRNA transcriptional read-through.[1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11]
Publication Abstract from PubMed
Shifts between epigenetic states of transcriptional activity are typically correlated with changes in epigenetic marks. However, exceptions to this rule suggest the existence of additional, as yet uncharacterized, layers of epigenetic regulation. MOM1, a protein of 2,001 amino acids that acts as a transcriptional silencer, represents such an exception. Here we define the 82 amino acid domain called CMM2 (Conserved MOM1 Motif 2) as a minimal MOM1 fragment capable of transcriptional regulation. As determined by X-ray crystallography, this motif folds into an unusual hendecad-based coiled-coil. Structure-based mutagenesis followed by transgenic complementation tests in plants demonstrate that CMM2 and its dimerization are effective for transcriptional suppression at chromosomal loci co-regulated by MOM1 and the siRNA pathway but not at loci controlled by MOM1 in an siRNA-independent fashion. These results reveal a surprising separation of epigenetic activities that enable the single, large MOM1 protein to coordinate cooperating mechanisms of epigenetic regulation.
Structural Basis of Transcriptional Gene Silencing Mediated by Arabidopsis MOM1.,Nishimura T, Molinard G, Petty TJ, Broger L, Gabus C, Halazonetis TD, Thore S, Paszkowski J PLoS Genet. 2012 Feb;8(2):e1002484. Epub 2012 Feb 9. PMID:22346760[12]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
References
- ↑ Amedeo P, Habu Y, Afsar K, Mittelsten Scheid O, Paszkowski J. Disruption of the plant gene MOM releases transcriptional silencing of methylated genes. Nature. 2000 May 11;405(6783):203-6. PMID:10821279 doi:http://dx.doi.org/10.1038/35012108
- ↑ Steimer A, Amedeo P, Afsar K, Fransz P, Mittelsten Scheid O, Paszkowski J. Endogenous targets of transcriptional gene silencing in Arabidopsis. Plant Cell. 2000 Jul;12(7):1165-78. PMID:10899982
- ↑ Mittelsten Scheid O, Probst AV, Afsar K, Paszkowski J. Two regulatory levels of transcriptional gene silencing in Arabidopsis. Proc Natl Acad Sci U S A. 2002 Oct 15;99(21):13659-62. Epub 2002 Oct 7. PMID:12370435 doi:http://dx.doi.org/10.1073/pnas.202380499
- ↑ Probst AV, Fransz PF, Paszkowski J, Mittelsten Scheid O. Two means of transcriptional reactivation within heterochromatin. Plant J. 2003 Feb;33(4):743-9. PMID:12609046
- ↑ Vaillant I, Schubert I, Tourmente S, Mathieu O. MOM1 mediates DNA-methylation-independent silencing of repetitive sequences in Arabidopsis. EMBO Rep. 2006 Dec;7(12):1273-8. Epub 2006 Nov 3. PMID:17082821 doi:http://dx.doi.org/10.1038/sj.embor.7400791
- ↑ Habu Y, Mathieu O, Tariq M, Probst AV, Smathajitt C, Zhu T, Paszkowski J. Epigenetic regulation of transcription in intermediate heterochromatin. EMBO Rep. 2006 Dec;7(12):1279-84. Epub 2006 Nov 3. PMID:17082818 doi:http://dx.doi.org/10.1038/sj.embor.7400835
- ↑ Caikovski M, Yokthongwattana C, Habu Y, Nishimura T, Mathieu O, Paszkowski J. Divergent evolution of CHD3 proteins resulted in MOM1 refining epigenetic control in vascular plants. PLoS Genet. 2008 Aug 22;4(8):e1000165. doi: 10.1371/journal.pgen.1000165. PMID:18725928 doi:http://dx.doi.org/10.1371/journal.pgen.1000165
- ↑ Yokthongwattana C, Bucher E, Caikovski M, Vaillant I, Nicolet J, Mittelsten Scheid O, Paszkowski J. MOM1 and Pol-IV/V interactions regulate the intensity and specificity of transcriptional gene silencing. EMBO J. 2010 Jan 20;29(2):340-51. doi: 10.1038/emboj.2009.328. Epub 2009 Nov 12. PMID:19910926 doi:http://dx.doi.org/10.1038/emboj.2009.328
- ↑ Mlotshwa S, Pruss GJ, Gao Z, Mgutshini NL, Li J, Chen X, Bowman LH, Vance V. Transcriptional silencing induced by Arabidopsis T-DNA mutants is associated with 35S promoter siRNAs and requires genes involved in siRNA-mediated chromatin silencing. Plant J. 2010 Nov;64(4):699-704. doi: 10.1111/j.1365-313X.2010.04358.x. Epub 2010, Oct 8. PMID:21070421 doi:http://dx.doi.org/10.1111/j.1365-313X.2010.04358.x
- ↑ Zhou Y, Zhang J, Lin H, Guo G, Guo Y. MORPHEUS' MOLECULE1 is required to prevent aberrant RNA transcriptional read-through in Arabidopsis. Plant Physiol. 2010 Nov;154(3):1272-80. doi: 10.1104/pp.110.162131. Epub 2010 Sep, 8. PMID:20826701 doi:http://dx.doi.org/10.1104/pp.110.162131
- ↑ Habu Y, Yoshikawa M. Locus-specific dependency of endogenous silent loci on MOM1 and non-CG methylation in Arabidopsis thaliana. Plant Signal Behav. 2010 Jun;5(6):724-6. Epub 2010 Jun 1. PMID:20404545
- ↑ Nishimura T, Molinard G, Petty TJ, Broger L, Gabus C, Halazonetis TD, Thore S, Paszkowski J. Structural Basis of Transcriptional Gene Silencing Mediated by Arabidopsis MOM1. PLoS Genet. 2012 Feb;8(2):e1002484. Epub 2012 Feb 9. PMID:22346760 doi:10.1371/journal.pgen.1002484
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