The gene for the common α subunit of porcine pituitary glycoprotein hormone

Abstract

ABSTRACT The gene for the common α subunit of the porcine anterior pituitary glycoprotein hormones was cloned from a genomic library constructed in EMBL3. The nucleotide sequence of the entire coding sequence of the porcine common α-subunit gene was determined in addition to one intron and 1059 and 160 bp of the 5′-and 3′-flanking regions respectively. Southern blot analysis of the porcine genomic DNA indicated that the common α-subunit gene is present as a single copy. The transcriptional unit of the porcine common α subunit spanned about 14kb and contained four exons interrupted by three introns of about 11.5, 1.2 and 0.4kb. The short untranslated sequence in the first exon and the location of the exon/intron junctions at amino acid residues +9/+10 and +71/+72 were highly conserved among the rat, human and bovine common α-subunit genes. In the proximal portion of the 5′-flanking region, one TATA box and one CCAAT box were present. A steroid-responsive element was not found up to 1059 bases upstream from the transcription start site. The potential AP-1 and AP-2 factor-responsive elements were present at three and one positions respectively in the 5′-flanking region. This feature suggests that hypothalamic gonadotrophin-releasing hormone stimulates the expression of the common α-subunit gene predominantly by a signal-transduction system, with the protein kinase C cascade and factors AP-1 and AP-2 as mediators. The cyclic AMP-responsive element was also present at two positions, but a single base substitution was found in each sequence compared with the consensus sequence. The porcine common α-subunit gene has a structure distinct from its counterparts, the porcine FSH-β and LH-β genes, reflecting differential control of their synthesis during gametogenesis.