Molecular characterisation of eIF4A paralogues

Dabrowska, Adrianna (2021) Molecular characterisation of eIF4A paralogues. PhD thesis, University of Glasgow.

Abstract

Translation dysregulation is a common occurrence in the tumour environment. In cancer cells, numerous regulatory features are perturbed to increase protein output and thus enhance cellular growth. This can be achieved either through overexpression of certain translational factors or dampening translation repression. Importantly, translation initiation is the crucial step at which most regulatory elements converge. Moreover, highly structured 5’UTRs of oncogenic mRNAs often require helicase activity in order to be translated. Interestingly, humans have two highly identical helicases, eIF4A1 and eIF4A2, which have been shown to not only promote different outcomes for cancer patients but also to have divergent translational roles. eIF4A1 is the canonical factor associated with eukaryotic translation initiation complex eIF4F, whereas eIF4A2 has been shown to interact with CCR4-NOT complex, and thus has been implicated in miRNAmediated translational repression.

The aim of this thesis was to understand what drives the distinct activities of the highly identical paralogues on a molecular level, and what influence the different interaction partners confer on the two helicases.

Using biochemical and structural approaches as well as cell imaging methods, the previously unexplored mechanisms that govern eIF4A2 and the distinct activities between the two paralogues were investigated.

The work presented in this thesis led to description and in-depth investigation of the novel RNA-dependent oligomeric formation of both paralogues. Most importantly, it was demonstrated that the potential to oligomerise dictates the catalytic properties of the paralogues, and that it is the RNA sequence and not the affinity that determines the extent of oligomerisation. Moreover, both helicases have different propensity to form oligomeric complexes. Additionally, regions responsible for divergent functions of eIF4A1 and eIF4A2 were identified. And the different functions imparted by their interaction partners were determined.

This study provides new understanding of the functions of eIF4A1 and eIF4A2 in the translational control and how functionally distinct oligomeric assemblies of the two paralogues can re-sculpture RNA landscapes.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Colleges/Schools: College of Medical Veterinary and Life Sciences > School of Cancer Sciences
• Supervisor's Name: Bushell, Professor Martin
• Date of Award: 2021
• Depositing User: Theses Team
• Unique ID: glathesis:2021-82593
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 09 Dec 2021 16:30
• Last Modified: 08 Apr 2022 17:09
• Thesis DOI: 10.5525/gla.thesis.82593
• URI: https://theses.gla.ac.uk/id/eprint/82593