Restructured transactivation domain in hamster AH receptor

Hamsters and Han/Wistar (Kuopio; H/W) rats show peculiarly selective respon siveness to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). They are extremely resistant to its acute lethality but sensitive to, e.g., enzyme induction. The biological effects of TCDD are mediated by the AH receptor (AHR). Recen t studies on H/W rat AHR discovered a remodelled transactivation domain whi ch appears to be critical for the TCDD resistance of these animals. Here, m olecular cloning and sequencing of hamster AHR reveals another type of rest ructured transactivation domain. In hamsters, the functionally pivotal Q-ri ch region is substantially expanded and enriched in glutamine compared with all other AHRs cloned to date. By contrast, the aminoterminal end is highl y conserved, which is in agreement with the H/W rat AHR. Because of the add itional material in the transactivation domain, hamster AHR protein is larg er than that in rats or mice, but the pattern of AHR mRNA expression in tis sues is similar. (C) 2000 Academic Press.