2 GENE DUPLICATION EVENTS IN THE HUMAN AND PRIMATE DOPAMINE D5 RECEPTOR GENE FAMILY

The human dopamine D5 receptor (DRD5) gene family consists of the DRD5 -encoding gene (DRDS) and the pseudogenes psi DRD5-1 and psi DRD5-2. A nalysis of the 5' UTR of DRD5 and homologous regions in the pseudogene s revealed that the nucleotide identity (approx. 95%) extended for 1.9 kb and terminated at a monomeric Alu sequence in each of the pseudoge nes. The presence of Alu sequences in the pseudogenes, at this point o f divergence with DRD5, suggests that Alu sequences were involved in t he evolution of the DRD5 family. This report is the first to describe a possible mechanism involved in the duplication of genes in the G-pro tein-coupled receptor (GPCR) family. The pseudogenes continue to share identity (approx, 98%) beyond this 5' UTR point of divergence with DR D5 for at least another 6 kb. Analysis of the 3' UTR of DRD5 and homol ogous regions in the pseudogenes revealed that the identity (approx. 9 5%) extends at least 14 kb, and the identity between the pseudogenes ( approx, 98%) extends for at least 18 kb. Thus, the duplication unit th at produced the first pseudogene was at least 16 kb, whereas the secon d pseudogene was at least 28 kb. We have also located two DRD5 pseudog enes in gorilla demonstrating that these closely related pseudogenes w ere present in a common ancestor of human and gorilla.