RNA Polymerase II subunit overexpression induces genome instability and deregulate transcription

Muste Sadurni, Martina ORCID: 0009-0003-2837-7803 (2024). RNA Polymerase II subunit overexpression induces genome instability and deregulate transcription. University of Birmingham. Ph.D.

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Abstract

Deregulated transcription is a well-established hallmark of cancer. However, studies on deregulations affecting the transcription complexes and specifically on RNA Polymerase II (Pol II) complex, remain elusive. In this work we propose the upregulation (defined as “PolUp” in this thesis) of the subunits POLR2A, POLR2C and POLR2D of Pol could constitute a new tumor biomarker, given the poor survival rates and increased genomic instability found in cancer patients baring at least one of the subunits upregulated. Using the HeLa T-REx inducible cell line model overexpressing the single subunit POLR2A,-2C or -2D, we investigated the consequences of subunits overexpressions on genome stability and transcription. Our finding suggest that each subunit overexpression impacts on DNA damage and transcription uniquely. By immunostaining and γH2AX ChIP-Seq we demonstrated that the overexpressions increase DNA damage formation and we identified the sites of damage. Furthermore, we hypothesised that the increased DNA damage is a result of transcription deregulations arising upon each subunit overexpression. We characterize nascent transcription by TT-chem-Seq and specific Pol II phosphorylation deregulations by ChIP-Seq and our findings suggest that even if there is a general increase in transcription activity, each subunit plays a different role on transcription regulation. Indeed, we identified Ser2 hyper phosphorylation and Ser5 hypo phosphorylation of Pol II CTD upon POLR2C and POLR2D overexpression, linked to a BRD4 and CDK7 defect, respectively. Finally, we were able to specifically target these deregulations with the BRD4 inhibitor JQ1 and the CDK7 inhibitor THZ1, showing how the mechanism identified to be responsible of transcription deregulations could be exploited for therapeutic purposes.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):