Abstract In eukaryotes, three RNA polymerases (RNAPs) play essential roles in the synthesis of various types of RNA: namely, RNAPI for rRNA; RNAPII for mRNA and most snRNAs; and RNAPIII for tRNA and Show more
Abstract In eukaryotes, three RNA polymerases (RNAPs) play essential roles in the synthesis of various types of RNA: namely, RNAPI for rRNA; RNAPII for mRNA and most snRNAs; and RNAPIII for tRNA and other small RNAs. All three RNAPs possess a short flexible tail derived from their common subunit RPB6. However, the function of this shared N-terminal tail (NTT) is not clear. Here we show that NTT interacts with the PH domain (PH-D) of the p62 subunit of the general transcription/repair factor TFIIH, and present the structures of RPB6 unbound and bound to PH-D by nuclear magnetic resonance (NMR). Using available cryo-EM structures, we modelled the activated elongation complex of RNAPII bound to TFIIH. We also provide evidence that the recruitment of TFIIH to transcription sites through the p62–RPB6 interaction is a common mechanism for transcription-coupled nucleotide excision repair (TC-NER) of RNAPI- and RNAPII-transcribed genes. Moreover, point mutations in the RPB6 NTT cause a significant reduction in transcription of RNAPI-, RNAPII- and RNAPIII-transcribed genes. These and other results show that the p62–RPB6 interaction plays multiple roles in transcription, TC-NER, and cell proliferation, suggesting that TFIIH is engaged in all RNAP systems. Show less
Significance RNAP1 transcription, dedicated to ribosomal DNAs (rDNAs), is the first and rate-limiting step of ribosome biogenesis. rDNAs are grouped into several copies. This redundancy is important t Show more
Significance RNAP1 transcription, dedicated to ribosomal DNAs (rDNAs), is the first and rate-limiting step of ribosome biogenesis. rDNAs are grouped into several copies. This redundancy is important to guarantee that at low damage levels one rDNA gene can be temporarily silenced without affecting overall ribosome biogenesis. Nevertheless, when DNA repair is defective or overloaded, several rDNAs could be damaged, disturbing the whole RNAP1 transcription process and later on modifying the ribosome content of cells. Therefore, it is of fundamental importance for the cell to maintain a functional RNAP1 transcription by repairing DNA lesions on rDNAs. In this work we identified, in mammals, the repair mechanism of rDNAs along with a specific behavior for RNAP1 after UV irradiation. Show less