RESUMO
Mammalian genomes encode a large number of non-coding RNAs (ncRNAs) that greatly exceed mRNA genes. While the physiological and pathological roles of ncRNAs have been increasingly understood, the mechanisms of regulation of ncRNA expression are less clear. Here, our genomic study has shown that a significant number of long non-coding RNAs (lncRNAs, >1000 nucleotides) harbor RNA polymerase II (Pol II) engaged with the transcriptional start site. A pausing and transcriptional elongation factor for protein-coding genes, tripartite motif-containing 28 (TRIM28) regulates the transcription of a subset of lncRNAs in mammalian cells. In addition, the majority of lncRNAs in human and murine cells regulated by Pol II promoter-proximal pausing appear to function in stimulus-inducible biological pathways. Our findings suggest an important role of Pol II pausing for the transcription of mammalian lncRNA genes.
Assuntos
Proteínas Nucleares/metabolismo , RNA Polimerase II/genética , RNA Longo não Codificante/genética , Proteínas Repressoras/metabolismo , Transcrição Gênica , Animais , Células Cultivadas , Regulação da Expressão Gênica , Genômica/métodos , Células HEK293 , Humanos , Mamíferos/genética , Camundongos , Células-Tronco Embrionárias Murinas/citologia , Regiões Promotoras Genéticas , RNA Polimerase II/metabolismo , Proteína 28 com Motivo TripartidoRESUMO
We have previously shown that RNA polymerase II (Pol II) pause release and transcriptional elongation involve phosphorylation of the factor TRIM28 by the DNA damage response (DDR) kinases ATM and DNA-PK. Here we report a significant role for DNA breaks and DDR signalling in the mechanisms of transcriptional elongation in stimulus-inducible genes in humans. Our data show the enrichment of TRIM28 and γH2AX on serum-induced genes and the important function of DNA-PK for Pol II pause release and transcriptional activation-coupled DDR signalling on these genes. γH2AX accumulation decreases when P-TEFb is inhibited, confirming that DDR signalling results from transcriptional elongation. In addition, transcriptional elongation-coupled DDR signalling involves topoisomerase II because inhibiting this enzyme interferes with Pol II pause release and γH2AX accumulation. Our findings propose that DDR signalling is required for effective Pol II pause release and transcriptional elongation through a novel mechanism involving TRIM28, DNA-PK and topoisomerase II.