A trimeric USP11/USP7/TCEAL1 complex stabilizes RNAPII during early transcription to sustain oncogenic gene expression

Abstract

During early transcription, RNA polymerase II (RNAPII) undergoes a series of structural transitions controlled by cyclin-dependent kinases. Whether protein ubiquitylation and proteasomal degradation affect the fate of RNAPII close to promoters is less well understood. Here we show that the deubiquitylating enzyme USP11 and its heterodimeric partner USP7 form a trimeric complex with TCEAL1, a member of the poorly understood TCEAL (TCEA/TFIIS-like) protein family. TCEAL1 shares sequence homology with the RNAPII interaction domain of the TCEA/TFIIS elongation factor, which controls the fate of backtracked RNAPII. TCEAL1 stabilizes complexes of USP11 with USP7 and with RNAPII. TCEAL1 is recruited to core promoters when transcription elongation is blocked and globally enhances the chromatin association of RNAPII during early transcription. Mechanistically, the USP11/USP7/TCEAL1 complex competes with TFIIS for binding to core promoters and protects RPB8, an essential subunit of RNAPII, from degradation, likely preventing excessive TFIIS-mediated transcript cleavage and RNAPII disassembly. In neuroblastoma and other tumors, TCEAL1-dependent genes define a TGF beta-dependent gene expression program that is characteristic for mesenchymal and invasive tumor cell types, suggesting that the USP11/USP7/TCEAL1 trimer stabilizes RNAPII during early transcription to support a critical oncogenic gene expression program (190 words).