Isolation and characterization of the human X-arrestin gene

Arrestins are signal transduction modulators that quench the activated stat e of receptors. X-arrestin (ARRX) is specifically expressed in the red-, gr een-, and blue-sensitive cone photoreceptors, and is most likely a modulato r of cone phototransduction. The human gene for X-arrestin at Xcen-Xq22 has been shown to be similar to 20 kb in size and to consist of 17 exons and 1 6 introns. The exons are generally small, including exon 16 of 10 bp, and a re clustered into three groups, separated by the two largest introns. This gene structure is generally similar to that of S-antigen, the rod photorece ptor arrestin. There is remarkable similarity, however, among the individua l exons between the two genes in that 10 of the exons are identical in size . The 5' upstream region of the X-arrestin gene contains TATA and CAAT boxe s, typical of genes expressed in a tissue-specific manner, in contrast to t he S-antigen gene, which lacks these promoter sequences. The promoter eleme nts, common to both the X-arrestin and S-antigen genes, include the Ret-1/P CE-1 (PCE-1-like in X-arrestin), CRX, and the thyroid hormone/retinoic acid -responsive sequences, the former two being present in a number of photorec eptor-expressed genes. Three CRX-binding elements, 15 bp apart, are present in a cluster. The common promoter elements between the cone-expressed gene s, X-arrestin and color opsins, include the TATA box, PCE-1, and CRX-bindin g sequences, the combination of which might be important for directing cone -specific expression. (C) 1998 Elsevier Science B.V. All rights reserved.