Department of Ophthalmology, Indiana University, Indianapolis 46202.
The human rod transducin alpha subunit (Tr alpha) gene has been cloned. A cDNA clone, HG14, contained a 1.1 kb insertion when compared with the human Tr alpha cDNA published by Van Dop et al. (1). Based on two overlapping clones isolated from a human genomic library, the human Tr alpha gene is 4.9 kb in length and consists of nine exons interrupted by eight introns. Northern blots of human retina total RNA showed that the gene is transcribed by rod photoreceptors into two species of mRNA, 1.3 kb and 2.4 kb in size. Apparently, this is the result of alternative splicing. Two putative transcription initiation sites were determined by primer extension and S1 nuclease protection assays. The putative promoter regions of the human and mouse Tr alpha genes have an identity of 78.1%. As found in the mouse gene (2), no TATA consensus sequence is present in the human gene.