UC Irvine

Internal ribosome entry sites (IRESs) are regions of mRNA that facilitate direct binding of components of the initiation complex for protein synthesis independent of the 5’-terminus. While first discovered in viruses, there are many cellular mRNAs that harbor these elements. The current study is evaluating the requirements (both canonical and non-canonical) for translation initiation on the voltage-gated potassium-channel (Kv1.4) IRES. Kv1.4 is a shaker related family member which contributes to the repolarizing phase of the cardiac action potential. Kv1.4 has a highly tissue-specific expression, despite its relatively non-specific promoter, and is regulated at the post-transcriptional level. Using both a genetic (yeast 3-hybrid screen) and a biochemical approach (biotinylated-RNA capture), we probed for novel interacting proteins that might modulate the activity of these IRES elements. Parallel screens reveal a diversity of interacting proteins, which may represent trans-acting factors for translation initiation. Gene set enrichment analysis as well as manual cross-reference identify a high abundance of RNA and translation associated proteins with and without ascribed functions in IRES-mediated translation. Characterizations of a select group of these interactions indicate roles in translation initiation and allude to tissue specific mechanisms of post-transcriptional regulation.