Human phosducin-like protein (hPhLP) messenger RNA stability is regulated by cis-acting instability elements present in the 3 '-untranslated region

Phosducin (Pd) and phosducin-like protein (PhLP) have been shown to regulat e G-protein signaling by binding G beta gamma subunits. To better define th e function and regulation of PhLP, and to begin to investigate its potentia l role in human pathophysiological states, we have cloned the human PhLP (h PhLP) cDNA. The hPhLP shows 92% identity with the rat PhLP (rPhLP). However , unlike the rPhLP, no evidence of hPhLP isoforms were detected in the huma n tissues investigated. Additionally, unlike the rPhLP, alternative polyade nylation sites were detected in hPhLP cDNA clones which corresponded with t wo distinct mRNA transcripts, 1.2 kb and 3.1 kb, respectively. Interestingl y, the predominantly expressed long transcript contains multiple AU-rich el ements (AREs) in its 3'-untranslated region (3'-UTR) which have been shown to correlate with rapid mRNA turnover and translational control. This study shows that the hPhLP AREs are functional both in vitro and in vivo, with t he long transcript exhibiting a much shorter mRNA half-life. We also demons trate that subcloning of either the full-length 3'-UTR or the ARE-rich regi on of the long transcript immediately following the stop codon of luciferas e reporter gene confers instability to the luciferase mRNA and results in a ninefold reduction of luciferase activity in the cell types investigated. Taken together, these findings suggest that the AREs present in the long hP hLP mRNA may play a critical role in the regulation of hPhLP gene expressio n. (C) 1999 Elsevier Science B.V. All rights reserved.