Poster abstracts

Poster number 10 submitted by Debmalya Bhattacharyya

Interaction between a G-quadruplex domain and 40s ribosomal subunit is critical for IRES A mediated translation initiation of hVEGF

Debmalya Bhattacharyya (Department of Chemistry and Biochemistry, Kent State University), Paige Diamond (Department of Biochemistry, Cell and Molecular Biology, Drake University), Soumitra Basu (Department of Chemistry and Biochemistry, Kent State University)

Abstract:
Human VEGF (hVEGF) is a mitogenic growth factor involved in both physiological and pathological angiogenesis. The 5′-untranslated region (UTR) of hVEGF mRNA is known to harbor two internal ribosomal entry site (IRESs), which under stress, are independently capable of initiating cap-independent translation. One of the IRESs, IRES A is a 293 nt sequence located towards the end of the 5′-UTR is responsible for cap-independent translation initiation at the canonical AUG start codon. The IRES A harbors a G-quadruplex (GQ) forming domain which is known to modulate cap-independent translation. G-quadruplex structures in the 5′-UTR of mRNA are known to regulate translation in general by inhibiting cap-dependent and augmenting cap-independent IRES mediated translation. The exact mechanism by which the GQ structures modulate the cap-independent translation is still unresolved. Our studies begin to shed light on the possible mechanistic role of GQ structures in cap-independent translation. We show here the direct interaction of a GQ structure in IRES A and it binds to the 40S ribosomal subunit with high affinity. The 40S ribosomal subunit binds to the 5′-proximal end of the IRES A which includes the GQ forming sequence. We also show that 40S subunit preferentially binds to the IRES in presence of the GQ structure with higher affinity. The GQ domain plays the most vital role in steering the IRES activity in a bicistronic plasmid in human cancer cells. The GQ in IRES A is an essential domain for the recruitment of 40S ribosomal subunit, which most likely is a key step for cap-independent initiation of translation.

References:
1. Bugaut, A.; Balasubramanian, S. Nucleic Acids Res 2012, 40, 4727.

2. Morris, M. J.; Negishi, Y.; Pazsint, C.; Schonhoft, J. D.; Basu, S. Journal of the American Chemical Society 2010, 132, 17831.

Keywords: G-quadruplex, IRES, hVEGF