Molecular cloning of cDNAs for precursors of porcine pituitary glycoprotein hormone common α-subunit and of thyroid stimulating hormone β-subunit

Abstract

cDNA clones encoding precursors of glycoprotein hormone common α-subunit (pre-α) and of thyroid stimulating hormone β-subunit (pre-TSHβ) were isolated from a porcine anterior pituitary cDNA library using DNA probes, and the nucleotide sequences were determined. The nucleotide sequence of pre-α cDNA contained an entire coding region (360 bases) including 5′ and 3′ untranslated regions. The pre-α mRNA was about 900 bases long. The predicted amino acid sequence consisted of a signal peptide of 24 amino acid residues and a mature α-subunit protein of 96 residues. Six amino acid residues at the amino terminus of the predicted mature protein had not been found by direct amino acid sequencing of the purified protein. The nucleotide sequence of pre-TSHβ cDNA contained an entire coding region and a 3′ untranslated region which has two polyadenylation signals. The length of the pre-TSHβ mRNA was about 500 bases long. The predicted amino acid sequence consisted of a signal peptide of 20 amino acid residues, a mature protein of 112 residues and an additional extension of six amino acid residues at the carboxyl terminus, which had not been found in the amino acid sequence of the purified protein. The coding sequences of the cDNAs showed high homologies with those of other mammalian species (84–93% for pre-α and 81–94% for pre-TSHβ). Comprehensive data of our serial molecular cloning for porcine glycoprotein hormones revealed low but significant homologies (34–40%) among three β-subunits. Upon comparison of frequency of (U) nA sequence in 3′ untranslated region, porcine pre-a and pre-TSH/J mRNAs were grouped into a moderate class of mRNA stability whereas porcine pre-FSHβ and pre-LHβ were grouped into unstable and stable classes, respectively.