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Lysine methyltransferase G9a is required for de novo DNA methylation and the establishment, but not the maintenance, of proviral silencing.
- Source :
-
Proceedings of the National Academy of Sciences of the United States of America [Proc Natl Acad Sci U S A] 2011 Apr 05; Vol. 108 (14), pp. 5718-23. Date of Electronic Publication: 2011 Mar 22. - Publication Year :
- 2011
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Abstract
- Methylation on lysine 9 of histone H3 (H3K9me) and DNA methylation play important roles in the transcriptional silencing of specific genes and repetitive elements. Both marks are detected on class I and II endogenous retroviruses (ERVs) in murine embryonic stem cells (mESCs). Recently, we reported that the H3K9-specific lysine methyltransferase (KMTase) Eset/Setdb1/KMT1E is required for H3K9me3 and the maintenance of silencing of ERVs in mESCs. In contrast, G9a/Ehmt2/KMT1C is dispensable, despite the fact that this KMTase is required for H3K9 dimethylation (H3K9me2) and efficient DNA methylation of these retroelements. Transcription of the exogenous retrovirus (XRV) Moloney murine leukemia virus is rapidly extinguished after integration in mESCs, concomitant with de novo DNA methylation. However, the role that H3K9 KMTases play in this process has not been addressed. Here, we demonstrate that G9a, but not Suv39h1 or Suv39h2, is required for silencing of newly integrated Moloney murine leukemia virus-based vectors in mESCs. The silencing defect in G9a(-/-) cells is accompanied by a reduction of H3K9me2 at the proviral LTR, indicating that XRVs are direct targets of G9a. Furthermore, de novo DNA methylation of newly integrated proviruses is impaired in the G9a(-/-) line, phenocopying proviral DNA methylation and silencing defects observed in Dnmt3a-deficient mESCs. Once established, however, maintenance of silencing of XRVs, like ERVs, is dependent exclusively on the KMTase Eset. Taken together, these observations reveal that in mESCs, the H3K9 KMTase G9a is required for the establishment, but not for the maintenance, of silencing of newly integrated proviruses.
- Subjects :
- Animals
Blotting, Western
Chromatin Immunoprecipitation
DNA (Cytosine-5-)-Methyltransferases genetics
Endogenous Retroviruses genetics
Flow Cytometry
Gene Silencing
Genetic Vectors genetics
Histone-Lysine N-Methyltransferase genetics
Mice
Mice, Knockout
Proviruses genetics
Reverse Transcriptase Polymerase Chain Reaction
DNA Methylation genetics
Embryonic Stem Cells virology
Histone-Lysine N-Methyltransferase metabolism
Moloney murine leukemia virus genetics
Subjects
Details
- Language :
- English
- ISSN :
- 1091-6490
- Volume :
- 108
- Issue :
- 14
- Database :
- MEDLINE
- Journal :
- Proceedings of the National Academy of Sciences of the United States of America
- Publication Type :
- Academic Journal
- Accession number :
- 21427230
- Full Text :
- https://doi.org/10.1073/pnas.1014660108