Alternative polyadenylation mediated shortening of the Hsp70.3 3′UTR increases polyribosome loading of the mRNA transcript

Abstract

IntroductionHeat shock protein 70.3 (Hsp70.3) expression is increased in response to cellular stress and plays a cytoprotective role, including a cardioprotective role in the heart against ischemia/reperfusion (I/R) injury. Recent work from our lab shows that Hsp70.3 expression following I/R is controlled through alternative polyadenylation (APA). Truncation of the 3′UTR removes potential regulatory sequences and is observed concomitant with upregulation of Hsp70.3 expression. Herein, we investigated the hypothesis that APA truncation of the 3′UTR enhances polysome loading of the Hsp70.3 transcript.MethodsSucrose gradient ultracentrifugation was used to isolate polysome bound mRNA from HL‐1 cardiac myocyte cells subjected to control (long 3′UTR) or a 1 hr heat shock (HS; short 3′UTR).ResultsCells subjected to HS for one hour showed a decrease in the total amount of polysome loaded mRNA. The Hsp70.3 transcript found in the polysome dense fractions existed as a higher ratio of the APA truncated short 3′UTR, thus supporting our hypothesis that APA truncation of the Hsp70.3 3′UTR increases polysome loading.Our results provide an enhanced understanding of APA on the regulation of Hsp70.3 and will have a significant impact in understating the regulation of cardiac gene regulation after I/R injury.This work was partially funded by a University of Cincinnati Provost Pilot Research Project grant (MT).