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The structure and function of a translation repression complex

   Faculty of Biological Sciences

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  Dr T A Edwards, Prof N A Ranson, Dr J Aspden  No more applications being accepted  Competition Funded PhD Project (European/UK Students Only)

About the Project

In Drosophila embryogenesis, Pumilio, Nanos and Brat come together in a multi-protein complex to recognise hunchback mRNA to repress translation only at the posterior end of the embryo, defining that end of the anterior-posterior axis. Translation is repressed when a cap binding protein, d4EHP, is recruited to compete with eIF4E to prevent cap mediated translation initiation. Human homologs of these proteins are involved in similar pathways, and in germ cell development and fertility. This project will investigate both the structure and the function of this multi-protein complex in repressing translation of selected target mRNAs.

Objectives and approaches
Dr Edwards has previously solved the crystal structures of domains of Pumilio and Brat, and relevant Nanos and d4EHP domains have been determined elsewhere. New information suggests an alternative model for assembly of the translation repression complex than previously thought, with Pumilio binding opening up a previously-occluded, novel, sequence-specific Brat binding site. The aim will be to express and purify Pumilio, Nanos and Brat proteins (+/- d4EHP), assemble the complex on RNA and attempt structure determination by both crystallisation of the components and of sub-complexes, and cryo-EM of the entire complex which may be too flexible to crystallise. High resolution crystal structures can of course be fitted into cryo-EM densities in a complementary approach. Note that the University of Leeds has recently invested ~£20M in new structural biology equipment, along with experienced support scientists, making it competitive with the best in the world. Atomic models generated by either cryo-EM or crystallography will suggest residues at the interfaces between proteins. These can be targeted for disruption in recombinant proteins and the effects tested in vitro, and the in vivo effects predicted and then tested using CRISPR technology.

Training environment
Supervisors are experts in molecular biology, Drosophila genetics and structural biology. Techniques to be employed include X-ray crystallography, cryo-electron microscopy and CRISPR/Cas9 generated Drosophila mutants.

What we offer
The successful applicant will join the Faculty of Biological Sciences Post-Graduate Research Program at the University of Leeds with other talented and motivated students passionate about research. The student will also join the Astbury Centre for Structural and Molecular Biology.

Applicant Requirements
Applicants should hold or expect a first/upper second-class honours degree or equivalent in a relevant subject with appropriate research experience and/or a Masters degree in a relevant subject. Knowledge of at least one of the following techniques is required (practical experience would be an advantage): protein expression and purification; electron microscopy imaging and data processing; X-ray crystallography.

Funding Notes

Project is eligible for funding under the FBS Faculty Studentships scheme. Successful candidates will receive a PhD studentship for 4 years, covering fees at UK/EU level and stipend at research council level (£14,777 for 2018-19).
Candidates should have, or be expecting, a 2.1 or above at undergraduate level in a relevant field. If English is not your first language, you will also be required to meet our language entry requirements. The PhD is to start in Oct 2018.
Please apply online here Include project title and supervisor name, and upload a CV and transcripts.


" Arvola RM, Weidmann CA, Tanaka Hall TM, Goldstrohm AC. Combinatorial control
of messenger RNAs by Pumilio, Nanos and Brain Tumor Proteins. RNA Biol. 2017 14(11):1445-1456.
" Loedige I, Jakob L, Treiber T, Ray D, Stotz M, Treiber N, Hennig J, Cook KB,
Morris Q, Hughes TR, Engelmann JC, Krahn MP, Meister G. The Crystal Structure of
the NHL Domain in Complex with RNA Reveals the Molecular Basis of Drosophila
Brain-Tumor-Mediated Gene Regulation. Cell Rep. 2015 13(6):1206-1220.
" Edwards TA Bespoke RNA recognition by Pumilios Biochemical Society Transactions 43 801-806, 2015
" Edwards TA, Wilkinson BD, Wharton RP, Aggarwal AK Model of the brain tumor-Pumilio translation repressor complex. Genes Dev 17 2508-2513, 2003
" Edwards TA, Pyle SE, Wharton RP, Aggarwal AK Structure of Pumilio reveals similarity between RNA and peptide binding motifs. Cell 105 281-289, 2001
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