A frequent restriction fragment length polymorphism in the human metallothionein-II processed gene region is evolutionarily conserved

Abstract

Genomic blot analysis of human DNA indicated that metallothioneins are represented by a multi-gene family. Clones containing metallothionein sequences have been isolated and two of these have been identified as metallothionein-I and metallothionein-II processed genes by sequence analysis. The metallothionein-II processed gene in humans shows two restriction fragment length polymorphisms of 4.5 and 4.8 kb (10³ bases) when EcoRI-digested genomic DNA from various individuals was analysed by Southern blotting. All the three genotypes are found at a high frequency and thus the metallothionein-II processed gene represents a true polymorphic marker. Familial studies also indicate that these restriction fragment length polymorphisms follow the classical Mendelian inheritance. Detailed Southern blot analyses show that this restriction fragment length polymorphism is due to a restriction site polymorphism and is localized at the 5'-flanking region of the metallothionein-II processed gene. Sequence analysis of the suspected region in the 4.8 kb fragment shows that the sequence G*GATTC, which is found 371 nucleotides downstream from the EcoRI site on the 5' end of the 4.8 kb fragment, makes a HinfI site. A transition of *G to A in this sequence in the 4.5 kb allele has resulted in loss of the HinfI site and created an EcoRI site. Thus, this mutation has given rise to this restriction fragment length polymorphism.