Project description:Histone H3K4 methylation is a feature of meiotic recombination hotspots shared by many organisms including plants and mammals. Meiotic recombination is initiated by programmed double strand break (DSB) formation that in budding yeast is directed in gene promoters by histone H3K4 di/trimethylation. This histone modification is indeed recognized by Spp1, a PHD-finger containing protein that belongs to the conserved histone H3K4 methyltransferase Set1 complex. During meiosis, Spp1 binds H3K4me and recruits a DSB protein, Mer2, to promote DSB formation close to gene promoters. How Set1C and Mer2 related functions of Spp1 are connected is not clear.
Project description:CXXC finger protein 1 (Cfp1) is a DNA-binding component of the SETD1 methyltransferase complex, targets SETD1A/B to most CpG islands (CpGI), and mediates the generation of H3K4me3. Deficiency of CFP1 in mice leads to pre-implantation lethality. Previous data suggest an indispensable role of CFP1 in germ cell development and meiosis. However, it remains unclear if CFP1-mediated H3K4 trimethylation is also required for the earliest stages of meiosis in both male and female germ cells. Here, we revealed that Cxxc1 deletion caused a decrease of H3K4me3 levels in spermatocytes after the zygotene stage, impaired double strand breaks (DSBs) repairing, and crossover formation in meiotic prophase. As the results, Cxxc1-deleted spermatocytes failed to complete meiosis and were arrested at the meiosis II. ChIP-seq results revealed that H3K4me3 globally descreased at transcriptional start sites in Cxxc1-null spermatocytes at the leptotene/zygotene and pathytene stages.RNA-seq at different stages revealed an earlier expression of genes within the spermatogenesis pathway in Cxxc1-null spermatocytes. These results indicated that CFP1 is required for H3K4me3 accumulation at the gene promoters of male germ cells and play a key role in regulating programed gene expression that is essential for spermatogenesis.
Project description:Monoubiquitination of histone H2B on lysine 123 (H2BK123ub) is a transient histone modification considered to be essential for establishing H3K4 and H3K79 trimethylation by Set1/COMPASS and Dot1, respectively. Many of the factors such as Rad6/Bre1, the Paf1 complex, and the Bur1/Bur2 complex were identified to be required for proper histone H3K4 and H3K79 trimethylation, and were shown to function by regulating H2BK123ub levels. Here, we have identified Chd1 as a factor that is required for proper maintenance of H2B monoubiquitination levels, but not for H3K4 and H3K79 trimethylation. Loss of Chd1 results in a substantial loss of H2BK123ub levels with little to no effect on the genome-wide pattern of H3K4 and H3K79 trimethylation. Our data shows that nucleosomal occupancy is reduced in gene bodies in both CHD1 null and K123A backgrounds. We have also demonstrated that Chd1’s function in maintaining H2BK123ub levels is conserved from yeast to human. Our study provides evidence that only small levels of H2BK123ub are necessary for full levels of H3K4 and H3K79 trimethylation in vivo, and points to a role for Chd1 in positively regulating gene expression through promoting nucleosome re-assembly coupled with H2B monoubiquitination. Examination of two histone modifications in wild-type and Chd1 null yeast strains using ChIP-seq. Expression profiling in wild-type and Chd1 null yeast strains using RNA-seq.
Project description:A decrease in oocyte developmental potential is a major obstacle for successful pregnancy in women of advanced age. However, the age-related epigenetic modifications associated with dynamic transcriptome changes, particularly meiotic maturation-coupled mRNA clearance, have not been adequately characterized in human oocytes. This study demonstrate a decreased storage of transcripts encoding key factors regulating the maternal mRNA degradome in fully grown oocytes of women of advanced age. A similar defect in meiotic maturation-triggered mRNA clearance was also detected in aged mouse oocytes. Mechanistically, the epigenetic and cytoplasmic aspects of oocyte maturation are synchronized in both the normal development and aging processes. The level of histone H3K4 trimethylation (H3K4me3) was high in fully grown mouse and human oocytes derived from young females but decreased during aging due to the decreased expression of epigenetic factors responsible for H3K4me3 accumulation. Oocyte-specific knockout of the gene encoding CxxC-finger protein 1 (CXXC1), a DNA-binding subunit of SETD1 methyltransferase, caused ooplasm changes associated with accelerated aging and impaired maternal mRNA translation and degradation. These results suggest that a network of CXXC1-maintained H3K4me3, in association with mRNA decay competence, sets a timer for oocyte deterioration and plays a role in oocyte aging in both mouse and human oocytes.
Project description:Monoubiquitination of histone H2B on lysine 123 (H2BK123ub) is a transient histone modification considered to be essential for establishing H3K4 and H3K79 trimethylation by Set1/COMPASS and Dot1, respectively. Many of the factors such as Rad6/Bre1, the Paf1 complex, and the Bur1/Bur2 complex were identified to be required for proper histone H3K4 and H3K79 trimethylation, and were shown to function by regulating H2BK123ub levels. Here, we have identified Chd1 as a factor that is required for proper maintenance of H2B monoubiquitination levels, but not for H3K4 and H3K79 trimethylation. Loss of Chd1 results in a substantial loss of H2BK123ub levels with little to no effect on the genome-wide pattern of H3K4 and H3K79 trimethylation. Our data shows that nucleosomal occupancy is reduced in gene bodies in both CHD1 null and K123A backgrounds. We have also demonstrated that Chd1’s function in maintaining H2BK123ub levels is conserved from yeast to human. Our study provides evidence that only small levels of H2BK123ub are necessary for full levels of H3K4 and H3K79 trimethylation in vivo, and points to a role for Chd1 in positively regulating gene expression through promoting nucleosome re-assembly coupled with H2B monoubiquitination.