BioProject

Chromatin is highly condensed and transcriptionally repressed during mitosis. More...

Chromatin is highly condensed and transcriptionally repressed during mitosis. Although it is established that some general transcription factors are inactivated by phosphorylation at mitosis, many details of mitotic transcriptional repression and its underlying mechanisms are largely unknown. Here, we provide evidence that as cells enter mitosis, genes with transcriptionally engaged RNA Polymerase II (Pol II) can continue transcription until the end of the gene to clear Pol II from mitotic chromatin. Using ChIP-Seq, we find that the transcriptional reinitiation process is globally impaired in early mitosis (prophase/prometaphase), with loss of TFIIB occupancy and nucleosome-free regions at promoters. Pretreatment of nocodazole-arrested mitotic cells with the P-TEFb inhibitor flavopiridol prevents the release of promoter-proximal engaged Pol II. Global nascent RNA sequencing and RNA fluorescence in situ hybridization (FISH) of individual genes demonstrate the existence of transcriptionally engaged Pol II in early mitosis. Chemical and mutational inhibition of P-TEFb in mitosis leads to delays in the progression of cell division. Together, our study reveals a novel mechanism for mitotic transcriptional repression whereby transcriptionally engaged Pol II can progress into productive elongation and finish transcription to allow proper cellular division. Overall design: ChIP-Seq of Pol II of different forms, TFIIB, H3K4me3 in human HeLa cells at different cell cycle stages. ChIP-Seq of Pol II in HeLa mitotic cells with or without CDK9 inhibitor flavopiridol pretreatment. Nascent RNA-seq in asynchronous and arrested mitotic cells. Less...