Poster abstracts

Poster number 51 submitted by Suman Govindaraju

Survival Mechanisms Involving Transcriptional Switch of HuR mRNA in Renal Stress

Suman Govindaraju (Physiology and Cell Biology), Dina Ayupova (Physiology and Cell Biology, Ohio State University)

Abstract:

HuR is an RNA binding protein that plays a protective role during cellular stress. The aims of our present study are to evaluate the regulation of HuR expression and mechanisms of transcriptional control. Previous studies in our lab demonstrated that HuR is expressed in two different forms, one of which contains an approximately 20 base 5’UTR sequence, and one that contains a 150 base G+C rich 5’UTR that is inhibitory to translation. Recovery of renal epithelia from cellular stress induced increased expression of the shorter, more translatable transcript and decreased expression of the longer form. While our lab has made progress in understanding mechanisms regulating transcription of the shorter mRNA, cellular mechanisms regulating the expression of the longer form are largely unknown. The goal of our study is to determine additional transcriptional regulators involved in the synthesis of these alternate HuR transcripts. Sequence analysis indicated that the 150 base, G+C-rich 5’UTR contains potential binding sites for transcriptional activators Sp1 and NF-κB. Our preliminary studies suggest that indeed over expression of these factors in proximal tubule cells increases levels of the long form of HuR mRNA. Gel shift assays and ribonuclease protection assays are being employed currently to confirm the role of these transcription factors in the transcriptional regulation of HuR.
Our in vivo model of rat kidneys is being utilized to test and evaluate the role of HuR in cellular protection during ischemia-reperfusion injury. HuR specific antisense oligonucleotides were injected into Sprague-Dawley rats prior to ischemia-reperfusion and protein and RNA levels of HuR were tested to evaluate the amount of HuR suppression and kidney function. Preliminary results indicate that specific knockdown of HuR in proximal tubule cells has a deleterious effect on kidney function. We will continue these studies to establish a functional role of HuR, which we hypothesize is critical modulator of pleiotropic effects mediated by bone morphogenetic proteins in mammalian kidneys.

Keywords: Stress, RNA binding proteins, Transcription