Molecular and cytogenetic characterization of a metallothionein gene of Drosophila.

A chromosomal DNA segment containing the metallothionein gene was isolated from a genomic library of Drosophila melanogaster using a previously characterized cDNA of this species as a probe. A segment of 1543 base pair (bp) was sequenced and found to include the cDNA sequence interrupted by one small intron. Several lines of evidence indicate that there is a single copy of the metallothionein gene (Mtn) in Drosophila; any other related genes, if they occur, must be sufficiently different that they are not detectable by our probe, even under hybridization conditions of reduced stringency. According to in situ hybridization and deletion mapping, Mtn is located in the right arm of the third chromosome in region 85E10-15. Within 300 bases upstream of the apparent site of transcription initiation, there are several short intervals very similar to the 12-bp segments considered to be responsible for metal regulation in mammalian systems.