Role of the RNA Polymerase II CTD-S2 phosphorylation by CDK-12 during the post-embryonic development in the nematode C. elegans

Student thesis: Doc typesDoctor of Sciences

Abstract

The C-terminal domain (CTD) of the RNA Polymerase II is composed of repeats of the consensus sequence Y1S2P3T4S5P6S7. The CTD is highly modified during transcription, which plays a major role in the coordination of transcription and mRNA maturation. CDK-12 phosphorylates the CTD-S2, a mark classically associated with elongation, splicing and cleavage/polyadenylation.
However, recent studies in yeast, fly and mammalian cell, highlighted a gene-specific requirement for CDK-12. For instance, in fission yeast, the CTD-S2 phosphorylation is only required for the induction of sexual differentiation.
In C. elegans, cdk-12 knockdown by RNAi results in a L1 arrest. The embryos hatch in presence of food but are unable to induce the post-L1 development, mimicking a L1 arrest in starvation. Homozygous cdk-12 disruption leads to the same terminal phenotype.
We have constructed an analog-sensitive (as) version of CDK-12, cdk-12as, to investigate the role of the CTD-S2 phosphorylation by CDK-12 during the early larval development. In the presence of low dose of the ATP analog, the cdk-12as strain arrests at the L1 stage with undetectable CTD-S2 phosphorylation. We show that the inhibition is specific, very fast, and can be reversed by washing out the ATP analogue.
Transcriptomic analyses by RNA-seq were performed during physiological or ATP analog-induced L1 arrest, which revealed that the loss of CDK-12 kinase activity only affects a subset of genes strongly enriched for “development related genes”. Deeper analyses indicated that most target genes belong to operons and undergo SL2 trans-splicing. Therefore, our results suggest that the CDK-12 kinase is specifically required for the induction of SL2-trans-spliced development related genes.
In addition, our data indicate that the RNA Polymerase II occupancy along the operons is barely affected when CDK-12 is inhibited, suggesting a posttranscriptional requirement, maybe during trans-splicing.
Taken together our results show that the phosphorylation of CTD-S2 by CDK-12 is dispensable during embryogenesis but is required to escape L1 arrest and pursue larval development.
Date of Award17 Mar 2017
LanguageEnglish
Awarding Institution
  • University of Namur
SponsorsFund for Research Training in Industry and Agriculture (FRIA)
SupervisorDamien Hermand (Supervisor), Olivier De Backer (President), Valérie Robert (Jury), Patrick Laurent (Jury) & René Rezsöhazy (Jury)

Keywords

  • RNA Polymerase II
  • CTD
  • C. elegans
  • transcription
  • Larval arrest
  • CDK-12

Attachment to an Research Institute in UNAMUR

  • NARILIS

Cite this

Role of the RNA Polymerase II CTD-S2 phosphorylation by CDK-12 during the post-embryonic development in the nematode C. elegans
Cassart, C. (Author). 17 Mar 2017

Student thesis: Doc typesDoctor of Sciences