Cloning and characterization of the human gene for the α-subunit of G_i2, a GTP-binding signal transduction protein

We isolated and characterized human genomic clones encompassing the gene for the α-subunit of G_i2, a GTP-binding signal transduction protein abundantly expressed in myeloid cells. The gene is divided into 9 exons and spans 23.5 kb. Exons 2, 6 and 7 encode putative guanine nucleotide-binding domains that are highly conserved among GTP-binding proteins. A polyadenylation signal located within exon 9 predicts an MRNA size (∼ 2.3 kb) several hundred bases longer than that of published cDNAs, and consistent with the size seen on RNA blot hybridization. Primer extension and S₁ nuclease analysis determined a major and several minor transcriptional start sites. The first exon and 5′ flanking region are highly G+ C rich, contain several GC boxes (SP1 transcription factor binding sites), a CAAT box, and lack a TATA box. The presumptive promoter region is thus similar to that of ras and other widely expressed genes.