Figure 3

Rhesus monkey inhibin α gene structure. Schematic representation of the genomic organization of the inhibin α subunit in rhesus monkey. Boxed regions reflect exons and the intervening straight line is the intron (the 2 kb is an estimate based on the 2051 bp intron in humans). Black boxes reflect 5' and 3' UTRs. White boxes reflect sequences encoding the signal peptide (in inhibin α-variant 1) or a domain of unknown function (inhibin α-variant 2). The other shaded regions correspond to the pro-α, αN, and αC domains of the inhibin α prepro-hormone and are labeled in the figure. Inhibin-α variant 1 is the canonical inhibin α mRNA described previously in other species and is produced through splicing of exons 1 and 2. Inhibin α-variant 2 is produced through splicing of the novel exon 0 and exon 2. In this latter form, the entirety of exon 1 is removed, in addition to intron 1. An A to G transition in the monkey genomic sequence (relative to the human sequence) at the end of exon 0 appears to introduce a GT 5' splice donor site, which is absent in other species. This allows the splicing event observed in inhibin α-variant 2 when an upstream transcription start site is utilized. This variant is not predicted to exist in other species and also appears to be rare in monkey. The approximate positions of the primers used in different RT-PCR analyses are shown. A and B refer to the forward and reverse primers, respectively, designed to amplify the final 465 bp of the open reading frame. C and D are the outer and inner gene specific reverse primers used in the 5' RACE procedure.