Isolation and characterization of the human Gs alpha gene

The gene for Gs alpha (the alpha subunit of the guanine nucleotide-binding protein Gs) was isolated from human genomic libraries using rat Gs alpha cDNA as a probe. Comparison of the nucleotide sequence of the human gene with that of the rat cDNA revealed that the human Gs alpha gene spans approximately equal to 20 kilobases and is composed of 13 exons and 12 introns. Genomic Southern blot analysis suggests that the human haploid genome contains a single Gs alpha gene. Previous reports indicated the presence of multiple species of Gs alpha cDNA. The structure of the human Gs alpha gene suggests that four types of Gs alpha mRNAs may be generated from a single Gs alpha gene by alternate use of exon 3 and/or of two 3' splice sites of intron 3, where an unusual splice junction sequence (TG) instead of the consensus (AG) is used. S1 nuclease mapping analysis of human Gs alpha mRNA identified multiple transcriptional initiation sites. The promoter region of the human Gs alpha gene has extremely high G + C content (85%). It contains 4 "GC" boxes, but no typical "TATA" or "CAAT" box sequence. In the 5' flanking region, there are several blocks of sequences that are similar to the sequences of the 5' flanking region of the human c-Ki-ras2 gene.