Dl. Lu et Kmj. Menon, 3'-UNTRANSLATED REGION-MEDIATED REGULATION OF LUTEINIZING-HORMONE HUMAN CHORIONIC-GONADOTROPIN RECEPTOR EXPRESSION, Biochemistry, 35(38), 1996, pp. 12347-12353
Multiple luteinizing hormone/human chorionic gonadotropin (LH/hCG) rec
eptor mRNAs (6.7, 4.4, 2.6, and 1.8 kb) have been identified in the ra
t ovary. Our laboratory has previously cloned a 3.5 kb cDNA that corre
sponds to the 3' untranslated region (3' UTR) of the 6.7 kb transcript
, the major LH/hCG receptor mRNA in rat ovary, In order to determine t
he effects of the 3' UTR on receptor expression, we have constructed c
DNAs corresponding to the open reading frame of LH/hCG receptor or luc
iferase, plus these constructs with the addition of the 3' UTRs associ
ated with the short (4.4 kb) and long (6.7 kb) LH/hCG receptor transcr
ipts, and measured receptor or luciferase expression in 293 cells tran
sformed with large T antigen (293T). Ligand binding analysis with I-12
5-hCG revealed that the 3' UTR inhibited receptor expression, which oc
curs through posttranscriptional events, First, the 3' UTRs reduced re
ceptor mRNA half-life in actinomycin D-arrested cells, as compared to
the open reading frame alone. Second, LH/hCG receptor mRNAs with the l
ong 3' UTR associated with significantly fewer ribosomes. The effect o
f the LH/hCG receptor 3' UTRs on luciferase expression was also determ
ined. The short 3' UTR increased luciferase activity, whereas the long
3' UTR decreased luciferase expression, Thus, the short 3' UTR exerts
opposite effects on receptor and luciferase expression. However, sequ
ences in the long 3' UTR are sufficient to inhibit both receptor and l
uciferase expression in 293T cells.