(647.1) DAP5 Binding to the FGF-9 mRNA 5’ UTR is Structurally-Dependent

Poster Board Number: A55

Amanda Whittaker (The Graduate Center, CUNY, The Graduate Center, CUNY), Dixie Goss (Hunter College, Hunter College)

Eukaryotic mRNA translation is typically modulated by eukaryotic initiation factor 4E (eIF4E) binding to the 5’-m7G cap. However, under the hypoxic conditions within the cancer cell, eIF4E is segregated by 4E binding protein. Thus, cap-independent recruitment of the 40S ribosome to the 5’ untranslated region (5’ UTR) of the mRNA is required for tumorigenesis. Fibroblast growth factor 9 (FGF-9) is one such angiogenic growth factor upregulated in a cap-independent manner in breast and colorectal cancer cells. Previously, our lab has demonstrated that binding of death-associated factor 5 (DAP5), a eukaryotic initiation factor, to the FGF-9 5’ UTR directly impacts cap-independent translational efficiency. However, the exact binding site of DAP5 within the 5’ UTR is unknown. RNA secondary and tertiary structure within non-coding regions has been demonstrated to play a role in cap-independent translational efficiency; therefore, we hypothesized that specific structures act as eukaryotic initiation factor binding sites. Using SHAPE-sequencing data, we reveal that the 5’ UTR of FGF-9 is highly structured and possesses a single-stranded region near the start codon. Through SHAPE footprinting and toeprinting experiments, we also demonstrate that DAP5 binds along a single face of the FGF-9 5’ UTR and contacts the 3’ single-stranded region. Our lab had previously reported that cap-independent translation of FGF-9 does not require a free 5’ end, suggesting little to no ribosomal scanning for the start codon occurs. Our current data demonstrate that initiation factor binding is structurally-dependent and suggest that limited ribosomal scanning is due to DAP5-dependent restructuring of the 5’ UTR to bring the start codon within striking distance of the 40S ribosome. We are currently examining whether cap-independent upregulation of other tumorigenic transcripts follows a similar pattern.

Support or Funding Information

NIH RO1 GM 128239

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