RESUMO
PRDM family members are transcriptional regulators involved in tissue specific differentiation. PRDM5 has been reported to predominantly repress transcription, but a characterization of its molecular functions in a relevant biological context is lacking. We demonstrate here that Prdm5 is highly expressed in developing bones; and, by genome-wide mapping of Prdm5 occupancy in pre-osteoblastic cells, we uncover a novel and unique role for Prdm5 in targeting all mouse collagen genes as well as several SLRP proteoglycan genes. In particular, we show that Prdm5 controls both Collagen I transcription and fibrillogenesis by binding inside the Col1a1 gene body and maintaining RNA polymerase II occupancy. In vivo, Prdm5 loss results in delayed ossification involving a pronounced impairment in the assembly of fibrillar collagens. Collectively, our results define a novel role for Prdm5 in sustaining the transcriptional program necessary to the proper assembly of osteoblastic extracellular matrix.
Assuntos
Desenvolvimento Ósseo/genética , Colágeno Tipo I , Osteoblastos , RNA Polimerase II/genética , Transcrição Gênica , Células 3T3 , Animais , Diferenciação Celular/genética , Colágeno Tipo I/genética , Colágeno Tipo I/metabolismo , Cadeia alfa 1 do Colágeno Tipo I , Proteínas de Ligação a DNA/genética , Proteínas de Ligação a DNA/metabolismo , Decorina/genética , Decorina/metabolismo , Desenvolvimento Embrionário/genética , Elementos Facilitadores Genéticos , Matriz Extracelular/genética , Matriz Extracelular/metabolismo , Colágenos Fibrilares , Regulação da Expressão Gênica no Desenvolvimento , Genoma , Camundongos , Especificidade de Órgãos , Osteoblastos/citologia , Osteoblastos/metabolismo , Regiões Promotoras Genéticas , Proteoglicanas/genética , Proteoglicanas/metabolismo , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismoRESUMO
The transcription factor PAX8 is critical for the development of the thyroid and urogenital system. Comprehensive genomic screens furthermore indicate an additional oncogenic role for PAX8 in renal and ovarian cancers. While a plethora of PAX8-regulated genes in different contexts have been proposed, we still lack a mechanistic understanding of how PAX8 engages molecular complexes to drive disease-relevant oncogenic transcriptional programs. Here we show that protein isoforms originating from the MECOM locus form a complex with PAX8. These include MDS1-EVI1 (also called PRDM3) for which we map its interaction with PAX8 in vitro and in vivo. We show that PAX8 binds a large number of genomic sites and forms transcriptional hubs. At a subset of these, PAX8 together with PRDM3 regulates a specific gene expression module involved in adhesion and extracellular matrix. This gene module correlates with PAX8 and MECOM expression in large scale profiling of cell lines, patient-derived xenografts (PDXs) and clinical cases and stratifies gynecological cancer cases with worse prognosis. PRDM3 is amplified in ovarian cancers and we show that the MECOM locus and PAX8 sustain in vivo tumor growth, further supporting that the identified function of the MECOM locus underlies PAX8-driven oncogenic functions in ovarian cancer.
Assuntos
Regulação Neoplásica da Expressão Gênica , Proteína do Locus do Complexo MDS1 e EVI1/genética , Neoplasias Ovarianas/genética , Fator de Transcrição PAX8/genética , Animais , Linhagem Celular Tumoral , Feminino , Células HEK293 , Humanos , Proteína do Locus do Complexo MDS1 e EVI1/metabolismo , Camundongos Nus , Neoplasias Ovarianas/tratamento farmacológico , Neoplasias Ovarianas/metabolismo , Fator de Transcrição PAX8/metabolismo , Ligação Proteica , Isoformas de Proteínas/genética , Isoformas de Proteínas/metabolismo , Carga Tumoral/genética , Ensaios Antitumorais Modelo de Xenoenxerto/métodosRESUMO
PRDM proteins belong to the SET domain protein family, which is involved in the regulation of gene expression. Although few PRDM members possess histone methyltransferase activity, the molecular mechanisms by which the other members exert transcriptional regulation remain to be delineated. In this study, we find that Prdm5 is highly expressed in mouse embryonic stem (mES) cells and exploit this cellular system to characterize molecular functions of Prdm5. By combining proteomics and next-generation sequencing technologies, we identify Prdm5 interaction partners and genomic occupancy. We demonstrate that although Prdm5 is dispensable for mES cell maintenance, it directly targets genomic regions involved in early embryonic development and affects the expression of a subset of developmental regulators during cell differentiation. Importantly, Prdm5 interacts with Ctcf, cohesin, and TFIIIC and cooccupies genomic loci. In summary, our data indicate how Prdm5 modulates transcription by interacting with factors involved in genome organization in mouse embryonic stem cells.