FUNCTIONAL COMPARISON OF THE METAL-REGULATED TRANSCRIPTIONAL CONTROL REGIONS OF METALLOTHIONEIN GENES FROM CADMIUM-SENSITIVE AND TOLERANT FISH SPECIES

摘要: The promoter region of teleost metallothioneins (MTs) contains multiple metal-responsive elements (MREs) organized in proximal and distal clusters which together mediate gene induction by heavy metals. This arrangement MREs is found both cadmium-sensitive species, such as the rainbow trout, cadmium-tolerant species pike stone loach. On comparison putative regulatory identified within 5'-flanking these genes major differences are that number differ between different that, while loach trout MT contain TATA boxes, has a TTTA box. In order to investigate if metal sensitivity correlated potential detoxification system regions from all three were assessed for their ability enhance transcription response metals Zn, Cd Cu. polymerase chain reaction was used produce nested deletion sets each cloned into mammalian expression vector pGL-2 upstream firefly luciferase gene. inducibility constructs challenge tested two cell lines, one fish line (homologous heterologous other species), hepatoma, RTH-149, studied human hepatoblastoma; HepG2, line. Maximum achieved with containing MRE clusters. Both showed comparable amplitude whilst on hand less inducible, partly due fewer These data indicate more than mechanism responsible cadmium species. Although main heavy-metal detoxifying most vertebrates appears be contributing seen pike, present study shows relative not primarily MT.