RAT GH RECEPTOR/GH-BINDING PROTEIN mRNAs KITH DIVERGENT 5′-UNTRANSLATED REGIONS ARE EXPRESSED IN A TISSUE- AND TRANSCRIPT-SPECIFIC MANNER

In the rat, the growth hormone receptor (GH-R) gene generates two transcripts, one that encodes for the GH-R, and a shorter one that encodes for the GH-binding protein (GH-BP). The mRNAs

encoding for these transcripts present a high degree of heterogeneity in the 5′ -untranslated regions (5′-UTR). It seems likely that some of the exons encoding 5′-UTR variants may be flanked

by distinct promoter regions. The activity of different promoters could result in the tissue-specific expression of these variants. To assess this possibility, we used PCR amplification to

characterize the 5′-UTR variants of rat GH-R mRNA, and by using 5′-UTR-specific probes, we determined their pattern of expression in several tissues in the rat. In addition to two previously

described variants (V1 and V2), three new 5′-UTR variants were identified, extending 56 nt. (V3), 135 nt. (V4), and 209 nt. (V5) upstream of the ATG translation initiation codon. The study

of tissue distribution revealed that variant V1 and V5 exhibited a pattern of expression resembling that of exon 2. Variant V2 was exclusively expressed in liver. Variant V4, although

present in liver, was more abundant in extrahepatic tissues, and predominantly found in GH-R transcripts. Variant V3 was expressed at low levels. These findings support the concept that

different 5′-UTR variants are the result of different promoters acting in a tissue-specific manner. The association of specific 5′-UTR variants with either GH-R or GH-BP mRNA transcripts

raises the possibility that the alternatively splicing process that generates GH-BP in the rat might be controlled by the 5′-flanking region driving specific leader exons.

Anyone you share the following link with will be able to read this content: