ABSTRACT: Histone H3 threonine 11 phosphorylation is catalyzed directly by the meiosis-specific kinase Mek1 and provides a molecular readout of Mek1 activity in vivo
Project description:Saccharomyces cerevisiae Mek1 is a CHK2/Rad53-family kinase that regulates meiotic recombination and progression upon its activation in response to DNA double-strand breaks (DSBs). The full catalog of direct Mek1 phosphorylation targets remains unknown. Here, we show that phosphorylation of histone H3 on threonine 11 (H3 T11ph) is induced by meiotic DSBs in S. cerevisiae and Schizosaccharomyces pombe. Molecular genetic experiments in S. cerevisiae confirmed that Mek1 is required for H3 T11ph and revealed that phosphorylation is rapidly reversed when Mek1 kinase is no longer active. Reconstituting histone phosphorylation in vitro with recombinant proteins demonstrated that Mek1 directly catalyzes H3 T11 phosphorylation. Mutating H3 T11 to nonphosphorylatable residues conferred no detectable meiotic defects, indicating that H3 T11ph is dispensable for Mek1 functions in controlling recombination. However, H3 T11ph provides an excellent marker of ongoing Mek1 kinase activity in vivo. Anti-H3 T11ph chromatin immunoprecipitation followed by deep sequencing demonstrated that H3 T11ph was highly enriched at presumed sites of attachment of chromatin to chromosome axes, gave a more modest signal along chromatin loops, and was present at still lower levels immediately adjacent to DSB hotspots. These localization patterns closely tracked the distribution of Red1 and Hop1, axis proteins required for Mek1 activation. These findings provide insight into the spatial disposition of Mek1 kinase activity and the higher order organization of recombining meiotic chromosomes.
Project description:We used ChIP-seq to determine the whole-genome enrichment of histone H3 threonine 11 phosphorylation (H3 T11ph) during Saccharomyces cerevisiae meiosis. S. cerevisiae SK1 cells were synchronized for meiotic entry and 3 and 4 hour meiotic samples were obtained. As H3 T11ph is dependent on the formation of meiotic double strand breaks (DSBs), a negative control ChIP-seq sample was obtained from a strain lacking DSBs (spo11-yf). Concurrently, ChIP-seq was carried out for histone H3 as a control for comparision.
Project description:Purpose: In this study, we show that DNA damage-activated AKT phosphorylates threonine 45 of core histone H3 (H3-T45) Result: By genome-wide chromatin immunoprecipitation sequencing (ChIP-seq) analysis, H3-T45 phosphorylation was distributed throughout DNA damage-responsive gene loci, particularly immediately after the transcription termination site Conclusion: AKT-mediated phosphorylation of H3-T45 regulates the processing of the 3′ end of DNA damage-activated genes to facilitate transcriptional termination MCF10A cells were ChIPed with anti-phosphorylated H3-T45, anti-phosphorylated RNA Pol II-S2 and S5, and anti-H3-K36me3.
Project description:Purpose: In this study, we show that DNA damage-activated AKT phosphorylates threonine 45 of core histone H3 (H3-T45) Result: By genome-wide chromatin immunoprecipitation sequencing (ChIP-seq) analysis, H3-T45 phosphorylation was distributed throughout DNA damage-responsive gene loci, particularly immediately after the transcription termination site Conclusion: AKT-mediated phosphorylation of H3-T45 regulates the processing of the 3′ end of DNA damage-activated genes to facilitate transcriptional termination
Project description:Meiosis is a specialized cell cycle that requires sequential changes to the cell division machinery to facilitate changing functions. To define the mechanisms that enable the oocyte-to-embryo transition, we performed time-course proteomics in sea star oocytes from prophase I through the first embryonic cleavage. Although protein levels are broadly stable, dynamic waves of phosphorylation underlie each meiotic stage. We find that the phosphatase PP2A-B55 is reactivated at the Meiosis I/II transition resulting in the preferential dephosphorylation of threonine residues. Selective dephosphorylation is critical for directing the MI / MII transition as altering PP2A-B55 substrate preferences disrupts key cell cycle events after meiosis I. In addition, threonine to serine substitution of a conserved phosphorylation site in the substrate INCENP prevents its relocalization at anaphase I. Thus, through its inherent phospho-threonine preference, PP2A-B55 imposes specific phosphoregulated behaviors that distinguish the two meiotic divisions.
Project description:BRAF, one of three RAF serine/threonine kinases (ARAF, BRAF and CRAF), plays a major role in the RAS-RAF-MEK-ERK mitogen-activated protein kinase (MAPK) signaling pathway, which mediates cellular responses to growth signals. Recently a high frequency (~60%-70%) of activating BRAF mutations (predominantly V600E) has been reported in malignant melanoma. In order to identify the downstream effects of BRAF signaling on melanoma cell growth and gene expression, cDNA microarray analysis was carried out following BRAF siRNA or MEK1/2 inhibitor (U0126) treatment. Keywords: time series, siRNA time series, siRNA, drug treatment
Project description:Protein phosphorylation, as one of the most important post-translational modifications, exerts crucial roles in regulating meiosis. However, there is a lack of systemic phosphoproteomic and functional analysis of phosphorylation in the meiosis of spermatocytes. To characterize the phosphorylation events in meiosis, we performed large-scale phosphoproteome profiling of purified spermatocytes undergoing meiosis, and identified 20,582 phosphorylation sites in 5,289 phosphoproteins, which were significantly enriched in cell cycle, autophagy, DNA repair, chromosome segregation. Kinase-substrate phosphorylation network analysis followed by in vitro meiosis study showed that CDK9 was a kinase with enriched substrate phosphorylation sites in spermatocytes, and was essential for meiosis progression to metaphase I. We also identified 15 new phosphorylation sites of histones, and 428 epigenetic factors, among which HASPIN was found to be essential for male fertility. Haspin knockout leaded to misalignment of chromosomes, apoptosis of metaphase spermatocytes and decreased number of sperm by deregulation of H3T3ph and Aurora-B kinase-containing chromosomal passenger complex. Our spermatocyte phosphoproteome will be a rich resource for future studies of phosphorylation signaling regulation of meiosis.
Project description:Cytochrome P450c17 (P450c17) is the single enzyme that catalyzes steroid 17alpha-hydroxylase and 17,20 lyase activities and hence is the crucial decision-making step that determines the class of steroid made in a steroidogenic cell. Although both activities are catalyzed on a single active site, the ratio of these activities is regulated by posttranslational events. Serine phosphorylation of P450c17 increases 17,20 lyase activity by increasing the enzyme's affinity for its redox partner, P450 oxidoreductase. We searched for the relevant kinase(s) that phosphorylates P450c17 by microarray studies and by testing of kinase inhibitors. Microarrays show that 145 of the 278 known serine/threonine kinases are expressed in human adrenal NCI-H295A cells, only six of which were induced more than 2-fold by treatment with 8-Br-cAMP. Key components of the ERK1/2 and MAPK/ERK kinase (MEK)1/2 pathways, which have been implicated in the insulin resistance of PCOS, were not found in NCI-H295A cells, implying that these pathways do not participate in P450c17 phosphorylation. Treatment with various kinase inhibitors that probe the protein kinase A/phosphatidylinositol 3-kinase/Akt pathway and the calcium/calmodulin/MAPK kinase pathway had no effect on the ratio of 17,20 lyase activity to 17alpha-hydroxylase activity, appearing to eliminate these pathways as candidates leading to the phosphorylation of P450c17. Two inhibitors that target the Rho-associated, coiled-coil containing protein kinase (ROCK)/Rho pathway suppressed 17,20 lyase activity and P450c17 phosphorylation, both in NCI-H295A cells and in COS-1 cells transfected with a P450c17 expression vector. ROCK1 phosphorylated P450c17 in vitro, but that phosphorylation did not affect 17,20 lyase activity. We conclude that members of the ROCK/Rho pathway act upstream from the kinase that phosphorylates P450c17 in a fashion that augments 17,20 lyase activity, possibly acting to catalyze a priming phosphorylation.
Project description:Drosophila Haspin kinase phosphorylates Histone H3 at threonine 3 at centromeric heterochromatin and either lamin- or polycomb-enriched euchromatic regions, being required for nuclear organization of interphase cells and polycomb-dependent gene silencing.