Poster abstracts

Poster number 82 submitted by Jeff Levengood

Physiochemical insights into an intrinsically disordered domain of hnRNP A1

Jeffrey D. Levengood (Case Western Reserve University, Department of Chemistry), Christopher E. Morgan (Case Western Reserve University, Department of Chemistry), Blanton S. Tolbert (Case Western Reserve University, Department of Chemistry)

Abstract:
The hnRNP A1 protein plays a key role in eukaryotic RNA processing events. It is composed of three domains, two structurally identical RRMs that form the nucleic acid binding protein UP1, and a disordered, glycine rich C-terminal domain (G-CTD).
As the more structured domain, UP1 has been studied extensively. Its RNA binding properties have been examined through numerous biochemical and biophysical methods. The G-CTD, which is a low complexity sequence domain, has not been very well characterized. The G-CTD is essential to the regulation of hnRNP A1 activity as it is responsible for protein-protein interactions with other regulatory proteins.
A preliminary view of the structure of full length hnRNP A1 has been obtained through SAXS-scored structural modeling. This model revealed the C-terminal domain to be a long, unstructured, disordered polypeptide chain extending away from the UP1 domain. This was confirmed by NMR HSQC data. When compared to full length hnRNP A1, the residues for UP1 showed minimal chemical shifts. Similar results were obtained for a comparison between full length hnRNP A1 and the G-CTD itself.
Recent research has shown the G-CTD to be a low complexity sequence domain (LCD) capable of mediating liquid-liquid phase separation (LLPS). This partitioning leads to the formation of stress granules, cytosolic bodies which are believed to be formed by mRNPs stalled in translation. The mRNA binding properties of hnRNP A1 provide it with the ability to sequester away stalled transcripts in this manner. In order to elucidate the role of hnRNP A1 in this process, we are studying the conditions under which it undergoes LLPS and the role RNA binding plays in mediating it. We have found LLPS is induced by low salt and low temperatures. The effects on LLPS in the presence of HIV-1 ESS3, a RNA structural element previously shown to regulate splicing, are also being examined.

Keywords: RRM, Stress Granules, Splicing Regulation