Universität zu Köln

Kochan, David Zygmunt (2020). Identification of a context-dependent Mpt5-mediated, post-transcriptional buffering system triggered by chromatin deregulation in S. cerevisiae. PhD thesis, Universität zu Köln.

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Abstract

The flow of genetic information from DNA to mRNA, and subsequent translation of the mRNA into protein, is essential for cell survival. Both transcriptional regulation at the chromatin level and post-transcriptional regulation of mRNA turnover work in a dynamic and coordinated manner to maintain this flow and proper cell function. Although these two levels of regulation clearly control gene expression together, there is very little information about a specific connection between the two levels of control. Therefore, the aim of this study was to establish if such a connection exists. We used an H3K56A histone mutant as a screening candidate. This mutant prevents a well-researched lysine acetylation that is as an important contributor to the maintenance of chromatin architecture and transcriptional regulation in Saccharomyces cerevisiae, yet it does not cause significant changes in steady state mRNA levels. To identify potential links between chromatin-templated processes and post-transcriptional control, H3K56A was crossed against a genomic deletion library using the synthetic genetic array approach. This led to the identification of a synthetic lethal genetic interaction between the Pumilio-family protein Mpt5 and H3K56A. Mpt5 is a diverse RNA binding protein that can target around 16% of the yeast transcriptome and has been shown to promote both degradation and buffering of transcripts. Further investigation into the MPT5-H3K56A interaction shows that loss of H3K56 acetylation triggers changes to nascent transcription, and Mpt5 buffers against these changes by stabilizing transcripts in a context-dependent manner, thus ensuring balanced steady-state mRNA levels. Depletion of Mpt5 in an H3K56A background results in a loss of this buffering system, causing a significant decrease in Mpt5 targets. Strikingly, these targets are strongly enriched for ribosomal protein transcripts. The observed down-regulation of ribosomal protein genes leads to a strong decrease in translation efficiency and ultimately, cell cycle arrest. We also provide further evidence that the Mpt5-mediated buffering system extends to other disturbances to chromatin architecture. We show that loss of H3K4 methylation can also trigger Mpt5 buffering, but most likely through a different mechanism. Therefore, in this study, we identify a mechanism linking chromatin dependent transcriptional control and post-transcriptional regulation of mRNA through a context-dependent, mRNA buffering system that is crucial to proper cell function.

Item Type:	Thesis (PhD thesis)
Translated title:	Title Language UNSPECIFIED English
Creators:	Creators Email ORCID ORCID Put Code Kochan, David Zygmunt dkochan@age.mpg.de UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-118746
Date:	27 August 2020
Language:	English
Faculty:	Faculty of Mathematics and Natural Sciences
Divisions:	Außeruniversitäre Forschungseinrichtungen > MPI for Biology of Ageing
Subjects:	Natural sciences and mathematics Life sciences
Uncontrolled Keywords:	Keywords Language H3K56ac, H3K56 acetylation, Mpt5, Puf5, nascent transcription, post-transcriptional buffering, context-dependent,H3K4me, H3K4 methylation, chromatin, buffering, English
Date of oral exam:	14 August 2020
Referee:	Name Academic Title Tessarz, Peter Dr. Riemer, Jan Prof. Dr.
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/11874