Project description:ChIP-Seq experiments targeting H3K4me2, H3K4me3, H3K9ac, H3K27ac, H3K36me3 histone modifications have been performed in order to assess if SETBP1 binding to gDNA was associated with chromatin remodeling and to further characterize the mechanisms responsible for SETBP1-mediated transcriptional regulation
Project description:PAX5 is a tumor suppressor in B-ALL, while the role of PAX5 fusion proteins in B-ALL development is largely unknown. Here we studied the function of PAX5-ETV6 and PAX5- FOXP1 in mice expressing these proteins from the Pax5 locus. Both proteins arrested Blymphopoiesis at the pro-B-to-pre-B cell transition and, contrary to their proposed dominantnegative role, did not interfere with the expression of most Pax5 target genes. Pax5-Etv6, but not Pax5-Foxp1, cooperated with loss of the Cdkna2a/b tumor suppressor in promoting B-ALL development. Regulated Pax5-Etv6 target genes identified in these B-ALLs encode proteins implicated in pre-BCR signaling and migration/adhesion, which could contribute to the proliferation, survival and tissue infiltration of leukemic B-cells. Together with similar observations made in human PAX5-ETV6+ B-ALLs, these data identified PAX5-ETV6 as a potent oncoprotein. 36 samples in total: A) 24 RNA-Seq samples in 5 cell types: pro-B (5 genotypes, 2-4 replicates) large pre-B (2 genotypes, 2 replicates each) small pre-B (1 genotype, 2 replicates) lymph node (1 genotype, 3 replicates) bone marrow (1 genotype, 2 replicates) B) 12 ChIP-Seq samples in 2 cell types: pro-B (H3K27me3, H3K9ac, H3K4me2, H3K4me3, H3K27ac, 1 replicate each; Pax5Etv6 ChIP, Prd ChIP, 2 replicates each; Pax5 ChIP 1 replicate) lymph node (1 genotype, 2 replicates).
Project description:FOXA1 is a pioneer factor that is important in hormone dependent cancer cells to stabilise nuclear receptors, such as estrogen receptor (ER) to chromatin. FOXA1 binds to enhancers regions that are enriched in H3K4mono- and dimethylation (H3K4me1, H3K4me2) histone marks and evidence suggests that these marks are requisite events for FOXA1 to associate with enhancers to initate subsequent gene expression events. However, exogenous expression of FOXA1 has been shown to induce H3K4me1 and H3K4me2 signal at enhancer elements and the order of events and the functional importance of these events is not clear. We performed a FOXA1 Rapid Immunoprecipitation Mass Spectrometry of Endogenous Proteins (RIME) screen in ERα-positive MCF-7 breast cancer cells in order to identify FOXA1 interacting partners and we found histone-lysine N-methyltransferase (MLL3) as the top FOXA1 interacting protein. MLL3 is typically thought to induce H3K4me3 at promoter regions, but recent findings suggest it may contribute to H3K4me1 deposition, in line with our observation that MLL3 associates with an enhancer specific protein. We performed MLL3 ChIP-seq in breast cancer cells and unexpectedly found that MLL3 binds mostly at non-promoter regions enhancers, in contrast to the prevailing hypothesis. MLL3 was shown to occupy regions marked by FOXA1 occupancy and as expected, H3K4me1 and H3K4me2. MLL3 binding was dependent on FOXA1, indicating that FOXA1 recruits MLL3 to chromatin. Motif analysis and subsequent genomic mapping revealed a role for Grainy head like protein-2 (GRHL2) which was shown to co-occupy regions of the chromatin with MLL3. Regions occupied by all three factors, namely FOXA1, MLL3 and GRHL2, were most enriched in H3K4me1. MLL3 silencing decreased H3K4me1 at enhancer elements, but had no appreciable impact on H3K4me3 at enhancer elements. We identify a complex relationship between FOXA1, MLL3 and H3K4me1 at enhancers in breast cancer and propose a mechanism whereby the pioneer factor FOXA1 can interact with a chromatin modifier MLL3, recruiting it to chromatin to facilitate the deposition of H3K4me1 histone marks, subsequently demarcating active enhancer elements.