Project description:Gene transcription is regulated by distant regulatory elements via combinatorial binding of transcription factors. It is increasingly recognized that alterations in chromatin state and transcription factor binding in these distant regulatory elements may have key roles in cancer development. Here we focused on the first stages of oncogene-induced carcinogenic transformation, and characterized the regulatory network underlying transcriptional changes associated with this process. Using Hi-C data, we observe spatial coupling between differentially expressed genes and their differentially accessible regulatory elements and reveal two candidate transcription factors, p53 and CTCF, as determinants of transcriptional alterations at the early stages of oncogenic HRas-induced transformation in human mammary epithelial cells. Strikingly, the malignant transcriptional reprograming is promoted by redistribution of chromatin binding of these factors without major variation in their expression level. Our results demonstrate that alterations in the regulatory landscape have a major role in driving oncogene-induced transcriptional reprogramming.
Project description:We report that the integration of the human papillomavirus into the host genome increases chromatin accessibility, transcription, and CTCF binding within 100 kbp of the integration site which promotes oncogenesis in some patients.
Project description:p53 is a pivotal tumor suppressor and a major barrier against cancer. We now report that silencing of the Hippo pathway tumor suppressors LATS1 and LATS2 in non-transformed mammary epithelial cells reduces p53 phosphorylation and increases its association with the p52 NF-κB subunit. Moreover, it partly shifts p53’s conformation and transcriptional output towards a state resembling cancer-associated p53 mutants, and endow p53 with the ability to promote cell migration. Notably, LATS1 and LATS2 are frequently downregulated in breast cancer; we propose that such downregulation might benefit cancer by converting p53 from a tumor suppressor into a tumor facilitator.
Project description:Tumor suppressors are mostly defined by inactivating somatic mutations in tumors, yet little is known about their epigenetic features in normal cells. Here, through integrative analysis of 1,134 genome-wide epigenetic profiles and mutations from >8,200 tumor-normal pairs, we discovered broad H3K4me3 (wider than 4 kb) as the first epigenetic signature for tumor suppressors in normal cells. Broad H3K4me3 is associated with increased transcription elongation and enhancer activity together leading to exceptionally high gene expression, and is distinct from other broad epigenetic features, such as super enhancers. Broad H3K4me3 conserved across normal cells represents core tumor suppressors, such as P53 and PTEN, whereas cell-type-specific broad H3K4me3 may indicate cell-identity genes and cell-type-specific tumor suppressors. Furthermore, widespread shortening of broad H3K4me3 in cancers is strongly associated with repression of tumor suppressors. Together, the broad H3K4me3 epigenetic signature we reported here may provide a new direction for the discovery and characterization of novel tumor suppressors. H3K4me3 ChIP-Seq was conducted in 1) liver tumor and matched tissue, 2) lung tumor and matched tissue, 3) cell line A549 grown under normal and flavopiridol treatment conditions.
Project description:The transcriptional profile of WapCre;Rank;Brca1;p53 and WapCre;Brca1;p53 mouse primary mammary tumor cells was determined by mRNA sequencing and uncovered differences in their molecular signatures including genes involved in oncogenesis, basic metabolism, RNA metabolism, or the regulation of mammary stem cells.
Project description:Tumor suppressors are mostly defined by inactivating somatic mutations in tumors, yet little is known about their epigenetic features in normal cells. Here, through integrative analysis of 1,134 genome-wide epigenetic profiles and mutations from >8,200 tumor-normal pairs, we discovered broad H3K4me3 (wider than 4 kb) as the first epigenetic signature for tumor suppressors in normal cells. Broad H3K4me3 is associated with increased transcription elongation and enhancer activity together leading to exceptionally high gene expression, and is distinct from other broad epigenetic features, such as super enhancers. Broad H3K4me3 conserved across normal cells represents core tumor suppressors, such as P53 and PTEN, whereas cell-type-specific broad H3K4me3 may indicate cell-identity genes and cell-type-specific tumor suppressors. Furthermore, widespread shortening of broad H3K4me3 in cancers is strongly associated with repression of tumor suppressors. Together, the broad H3K4me3 epigenetic signature we reported here may provide a new direction for the discovery and characterization of novel tumor suppressors.