Sequence analysis of cDNA encoding rabbit follicle-stimulating hormone β-subunit precursor protein

To understand the molecular basis of the rabbit’s efficient superovulation, we determined the cDNA sequence of the follicle-stimulating hormone (FSH) β-subunit precursor protein using a combination of 5′- and 3′-rapid amplification of cDNA ends (RACE) with pituitary cDNA libraries of the Japanese White rabbit and compared it with those of other mammals. RACE experiments detected at least three transcripts for the FSHβ precursor protein in the libraries. The transcripts had lengths of 457, 1621, and 1767 bp, from the 5′-end to the poly(A) site. The shortest and mid-length transcripts had the putative polyadenylation signal sequence AATAAA at nucleotides 436 and 1601, respectively, whereas the longest form had an ATTAAA sequence at nucleotide 1745 of the cDNA sequence. These transcripts are likely to be polyadenylation variants of one large transcript because they share the same coding sequence for the precursor protein (130 amino acid residues in length). However, only a few shortest variants seem to be formed because the shortest variants were not detected by Northern blot analysis. Phylogenetic analysis of the deduced amino acid sequence indicates that the rabbit is phylogenetically closer to humans than to the other mammals, suggesting that an FSH preparation from human sources would be superior as a follicle stimulant for the induction of superovulation.