The RNA Polymerase II factor RPAP1 is critical for Mediator-driven transcription and cell identity
The RNA polymerase II-associated protein 1 (RPAP1) is conserved across metazoa and required for stem cell differentiation in plants; however, very little is known about its mechanism of action or its role in mammalian cells. Here, we report that RPAP1 is essential for the expression of cell identity genes and for cell viability. Depletion of RPAP1 triggers cell de-differentiation, facilitates reprogramming toward pluripotency, and impairs differentiation. Mechanistically, we show that RPAP1 is essential for the interaction between RNA polymerase II (RNA Pol II) and Mediator, as well as for the recruitment of important regulators, such as the Mediator-specific RNA Pol II factor Gdown1 and the C-terminal domain (CTD) phosphatase RPAP2. In agreement, depletion of RPAP1 diminishes the loading of total and Ser5-phosphorylated RNA Pol II on many genes, with super-enhancer-driven genes among the most significantly downregulated. We conclude that Mediator/RPAP1/RNA Pol II is an ancient module, conserved from plants to mammals, critical for establishing and maintaining cell identity. ; Spanish Ministry of Economy co-funded by the EuropeanRegional Development Fund (ERDF) (SAF2013-48256-R), the EuropeanResearch Council (ERC-2014-AdG/669622), the Regional Government of Ma-drid co-funded by the European Social Fund (ReCaRe project), the EuropeanUnion (RISK-IR project), the Botin Foundation and Banco Santander(Santander Universities Global Division), the Ramon Areces Foundation, andthe AXA Foundation. S.R. was funded by a contract from the Ramon y CajalProgram(RYC-2011-09242) and by the Spanish Ministry of Economy co-funded by the ERDF (SAF2013-49147-P and SAF2016-80874-P). ; Peer reviewed
