The 3'-untranslated region of the beta2-adrenergic receptor mRNA regulates receptor synthesis.
beta(2)-Adrenergic receptors (beta(2)-ARs) are low abundance integral membrane proteins that mediate the effects of catecholamines at the cell surface. Post-transcriptional regulation of beta(2)-AR is dependent, in part, on sequences within the 5'- and 3'-untranslated regions (UTRs) of the receptor mRNA. In this work, we demonstrate that 3'-UTR sequences regulate the translation of the receptor mRNA. Deletion of the 3'-UTR sequences resulted in 2-2.5-fold increases in receptor expression. The steadystate levels of beta(2)-AR mRNA did not change significantly in the presence or absence of the 3'-UTR, suggesting that the translation of the receptor mRNA is suppressed by 3'-UTR sequences. Introduction of the receptor 3'-UTR sequences into the 3'-UTR of a heterologous reporter gene (luciferase) resulted in a 70% decrease in reporter gene expression without significant changes in luciferase mRNA levels. Sucrose density gradient fractionation of cytoplasmic extracts from Chinese hamster ovary cells transfected with full-length receptor cDNA demonstrated that the receptor transcripts were distributed between polysomal and non-polysomal fractions. Deletion of 3'-UTR sequences from the receptor cDNA resulted in a clear shift in the distribution of receptor mRNA toward the polysomal fractions, favoring increased translation. The 3'-UTR sequences of the receptor mRNA were sufficient to shift the distribution of luciferase mRNA from predominantly polysomal fractions toward non-polysomal fractions in cells transfected with the chimeric luciferase construct. Taken together, our results provide the first evidence for translational control of beta(2)-AR expression by 3'-UTR sequences. Presumably, this occurs by affecting the receptor mRNA localization.
Subramaniam
Kothandharaman
K
Department of Medicine and the Division of Nephrology, Medical University of South Carolina, Charleston, South Carolina 29425-2221, USA.
Chen
Kenneth
K
Joseph
Kusumam
K
Raymond
John R
JR
Tholanikunnel
Baby G
BG
D020413:3' Untranslated Regions / Q000235:genetics / Q000502:physiology*; D000818:Animals; D016466:CHO Cells; D002460:Cell Line; D006224:Cricetinae; D003412:Cricetulus; D018076:DNA, Complementary / Q000235:genetics; D040461:Gene Components / Q000235:genetics; D017353:Gene Deletion; D017930:Genes, Reporter / Q000235:genetics; D006801:Humans; D008156:Luciferases / Q000235:genetics; D011132:Polyribosomes / Q000378:metabolism; D014176:Protein Biosynthesis / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics* / Q000502:physiology; D018343:Receptors, Adrenergic, beta-2 / Q000096:biosynthesis* / Q000235:genetics; D014162:Transfection
D020413:3' Untranslated Regions; D018076:DNA, Complementary; D012333:RNA, Messenger; D018343:Receptors, Adrenergic, beta-2; D008156:Luciferases