Gene Regulation by Decapping and Cap Methylation of Mammalian mRNAs

• Applicant: Dr. Johanna Mattay
• Subject Area: General Genetics and Functional Genome Biology ; Biochemistry
• Term: from 2018 to 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 412011717

The processing of the messenger RNA (mRNA) is crucial for an efficient gene expression in the eukaryotic cell. A chemical modification at the 5ʹ end of the mRNA is the cap structure. This 5ʹ cap is installed on every mRNA strand generated during transcription. It stabilizes the mRNA and is required for further translation of the mRNA-sequence to functional proteins. The removal of the 5ʹ cap has adverse effects: the mRNA-strand is destabilized and degraded, and thus translation to proteins is impeded. The excision of the 5ʹ cap is catalysed by decapping enzymes: the m7G-cap (N7-methyl guanosine) is hydrolysed by the enzyme Dcp2. In recent years, additional decapping enzymes have been identified in the Nudix family of hydrolases. However, little is known about putative interaction partners or the physiological roles of the Nudix decapping enzymes. Our central question is: How do decapping enzymes regulate the expression of specific genes to functional proteins? How does the cell ‘decide’ whether to preserve or to destroy an mRNA-transcript through the action of decapping? In this study, we aim to investigate the mammalian Nudix enzymes for their decapping activity and how this influences mRNA processing, maintenance, and decay. It is also conceivable that novel 5ʹ cap structures can be uncovered. We use a combination of biochemical, analytical, and RNA-sequencing techniques to identify mRNA targets of Nudix proteins. These will be validated in mutant cell lines harbouring inactivated Nudix enzymes, and protein complex partners will be identified. The physiological roles of one of the Nudix enzymes will be examined in mouse mutants.The host lab of Ramesh Pillai is focussing on the analysis of RNA modifications such as methylation; I am proficient in the characterisation of hydroxylases and demethylases. This expertise can be combined to study the decapping enzymes under a unique aspect: the impact of mRNA modifications. Our special aim is to address a potential interplay between mRNA decapping and reversible mRNA methylation/demethylation. Modifications in the cap structure such as N6- or 2ʹ-O-methylation in adenine can influence the activity of both decapping enzymes and demethylases, which may be interdependent. Primarily, I am interested in the catalysis of mRNA decapping enzymes and their physiological relevance in mammals. Additionally, a plausible impact of mRNA (de)methylation on the control of decapping enzymes will be investigated. This work may shed light on the complex mRNA regulatory pathways in their entirety.

• DFG Programme: Research Fellowships
• International Connection: Switzerland
• Host: Professor Ramesh S. Pillai, Ph.D.