Drosophila STAM is a homolog of mammalian STAM genes, which encode Jak associated signal-transducing adapter molecules. A 20-kilobase stretch of genomic DNA at 32B on chromosome arm 2L, which contains Drosophila STAM, has been sequenced. By comparison to cDNAs isolated and characterized, this region contains four tightly clustered genes: ial, mitochondrial porin, and the two newly discovered genes, STAM and DNZ1. Like its mouse and human homologs, STAM bears SH3 and ITAM domains. DNZ1 is a founding member of a sub-family of proteins bearing a DHHC/NEW1 zinc finger domain. Although these four genes are contained in a defined Deficiency overlap interval, no available P-element mutations in the region disrupt any of the genes, and no other discrete mutations in the genes have been identified. Among the four genes, ial and STAM share a common 5' control region, suggesting coordinate expression. Developmental Northern data and embryonic and ovariole expression data show that STAM and ial expression are correlated. The other two genes in the cluster appear to be expressed at constitutive levels throughout development.