STRUCTURE AND EXPRESSION OF 2 HIGHLY RELATED GENES ENCODING SCM-1 HUMAN LYMPHOTACTIN

SCM-1/lymphotactin is a chemokine-like molecule produced selectively, if not exclusively, by activated CD8(+) T cells. Here we report that t here are two highly homologous SCM-1 genes, which we designate as SCM- 1 alpha and SCM-1 beta. Both genes have three exons and two introns. T he 1st intron of SCM-1 alpha contains a pseudogene of the ribosomal la rge subunit L7a. In SCM-1 beta, a 1.5-kb region including about a quar ter of the L7a pseudogene is deleted from the 1st intron, Otherwise, t he two genes are highly homologous including the 5' and 3' flanking re gions, Both genes were mapped to human chromosome 1q23, The two genes were similarly induced in peripheral blood mononuclear cells by mitoge nic stimulation, Primer extension and RNase protection revealed severa l transcription initiation sites, The biological activities of SCM-1 a lpha and SCM-1 beta, which hare two amino acid differences at position s 7 and 8 in the mature proteins, remain to be compared.