Nucleotide sequence of the third cytokine LD78 gene and mapping of all three LD78 gene loci to human chromosome 17

Abstract

Cytokine LD78 is a member of a newly identified cytokine superfamily. We cloned the third human gene for the LD78, termed LD78γ and the sequence analysis showed that it is a 5′-truncated pseudogene. Exons 2 and 3 and the intron between them are highly homologous to those of the LD78β gene, hence, the γ gene was probably derived from the β gene. Southern blot analysis of humanxmouse somatic hybrid cell DNAs and in situ hybridization experiments mapped all the three gene loci on human chromosome 17q21.1-q21.3. Analysis of DNAs from family members supports our previous finding that the β and γ genes on each of the paired chromosome 17 vary in copy number and that the LD78α gene is presumably a single copy. In our analyses of cosmid clones, the LD78β gene and the second gene for AT744, which is also a member of the superfamily are closely linked in a head-to-head arrangement. The mechanism of generation of the three LD78 genes is discussed.

Key Words:

• chromosome 17
• cytokine family
• LD78γ pseudogene