ABSTRACT
Heterochromatin is required to restrict aberrant expression of retrotransposons, but it remains poorly defined due to the underlying repeat-rich sequences. We dissected Suv39h-dependent histone H3 lysine 9 trimethylation (H3K9me3) by genome-wide ChIP sequencing in mouse embryonic stem cells (ESCs). Refined bioinformatic analyses of repeat subfamilies indicated selective accumulation of Suv39h-dependent H3K9me3 at interspersed repetitive elements that cover â¼5% of the ESC epigenome. The majority of the â¼8,150 intact long interspersed nuclear elements (LINEs) and endogenous retroviruses (ERVs), but only a minor fraction of the >1.8 million degenerate and truncated LINEs/ERVs, are enriched for Suv39h-dependent H3K9me3. Transcriptional repression of intact LINEs and ERVs is differentially regulated by Suv39h and other chromatin modifiers in ESCs but governed by DNA methylation in committed cells. These data provide a function for Suv39h-dependent H3K9me3 chromatin to specifically repress intact LINE elements in the ESC epigenome.
Subject(s)
Embryonic Stem Cells/enzymology , Endogenous Retroviruses/genetics , Gene Silencing , Histone-Lysine N-Methyltransferase/physiology , Histones/metabolism , Long Interspersed Nucleotide Elements , Methyltransferases/physiology , Repressor Proteins/physiology , Animals , Cells, Cultured , DNA Methylation , Mice , Protein Processing, Post-TranslationalABSTRACT
We analyzed the levels of acetylated histones and histone H3 dimethylated on lysine 4 (H3K4me2) at the LMP2A promoter (LMP2Ap) of Epstein-Barr virus in well-characterized type I and type III lymphoid cell line pairs and additionally in the nasopharyngeal carcinoma cell line C666-1 by using chromatin immunoprecipitation. We found that enhanced levels of acetylated histones marked the upregulated LMP2Ap in lymphoid cells. In contrast, in C666-1 cells, the highly DNA-methylated, inactive LMP2Ap was also enriched in acetylated histones and H3K4me2. Our results suggest that the combinatorial effects of DNA methylation, histone acetylation, and H3K4me2 modulate the activity of LMP2Ap.
Subject(s)
DNA, Viral/chemistry , Herpesvirus 4, Human/physiology , Histones/analysis , Lymphocytes/virology , Promoter Regions, Genetic , Viral Matrix Proteins/biosynthesis , Acetylation , Cell Line, Tumor , Chromatin Immunoprecipitation , Herpesvirus 4, Human/chemistry , Humans , Lymphocytes/chemistry , Methylation , Molecular Sequence Data , Protein Binding , Viral Matrix Proteins/geneticsABSTRACT
Heterochromatin is important for genome integrity and stabilization of gene-expression programs. We have identified the transcription factors Pax3 and Pax9 as redundant regulators of mouse heterochromatin, as they repress RNA output from major satellite repeats by associating with DNA within pericentric heterochromatin. Simultaneous depletion of Pax3 and Pax9 resulted in dramatic derepression of major satellite transcripts, persistent impairment of heterochromatic marks and defects in chromosome segregation. Genome-wide analyses of methylated histone H3 at Lys9 showed enrichment at intergenic major satellite repeats only when these sequences retained intact binding sites for Pax and other transcription factors. Additionally, bioinformatic interrogation of all histone methyltransferase Suv39h-dependent heterochromatic repeat regions in the mouse genome revealed a high concordance with the presence of transcription factor binding sites. These data define a general model in which reiterated arrangement of transcription factor binding sites within repeat sequences is an intrinsic mechanism of the formation of heterochromatin.
Subject(s)
Heterochromatin/metabolism , Paired Box Transcription Factors/metabolism , Animals , Base Sequence , Binding Sites , Cell Cycle/genetics , Chromosome Segregation , DNA, Satellite/metabolism , Fibroblasts/metabolism , Genome , Heterochromatin/genetics , Histones/metabolism , Lysine/metabolism , Methylation , Methyltransferases/genetics , Methyltransferases/metabolism , Mice , Mice, Mutant Strains , Molecular Sequence Data , PAX3 Transcription Factor , PAX5 Transcription Factor/genetics , PAX5 Transcription Factor/metabolism , PAX7 Transcription Factor/genetics , PAX7 Transcription Factor/metabolism , PAX9 Transcription Factor , Paired Box Transcription Factors/genetics , Repressor Proteins/genetics , Repressor Proteins/metabolismABSTRACT
Herpes simplex virus type 2 infection is a quite common but frequently asymptomatic, therefore undiagnosed condition. Genital HSV-2 infection may cause neonatal herpes, enhances HIV transmission and may play a role in infertility. To evaluate the prevalence of HSV-2 in Hungary we tested 2500 serum samples for the presence of anti-HSV-2 IgG by ELISA method. According to our results Hungary belongs to the low-infected countries, the HSV-2 seroprevalence grows with age and is significantly higher among women than in men. We also examined the serostatus of 512 pregnant women and 539 women attending infertility clinics. Results show that the HSV-2 prevalence is significantly higher among women attending infertility clinics and the seropositivity of pregnant women is similar to that of the general Hungarian women population with the same age.