THE MOUSE RELAXIN-LIKE FACTOR GENE AND ITS PROMOTER ARE LOCATED WITHIN THE 3'-REGION OF THE JAK3 GENOMIC SEQUENCE

Isolation and sequencing of a genomic clone encoding the mouse gene fo r the relaxin-like factor (RLF), which is endogenously expressed to a high level exclusively in Leydig cells, indicated that similar sequenc es mere also present at the 3' end of the mouse JAK3 gene, a gene expr essed predominantly in lymphoid tissues, More extensive Southern blot, polymerase chain reaction and sequencing analyses showed that the pub lished mouse sequence for exon 23 of the JAK3 gene in fact comprises t wo exons, 23A and 23B, separated by an additional novel intron of 2.2 kb, and that within this intron the promoter and exon 1 of the mouse R LF gene are encoded, The two overlapping transcripts appear to use dif ferent polyadenylation signals in the common 3' untranslated region of exon 23B, Transient transfection of different RLF promoter reporter c onstructs into Leydig, Sertoli, granulosa and kidney cell lines indica te that as little as 0.7 kb of the region upstream of exon I of the RL F gene, and within the novel intron 22 of the JAK3 gene, is sufficient to account for cell-specific expression of the RLF gene, This promote r region is specifically hypomethylated in Leydig cells compared to no n-expressing tissues. (C) 1997 Federation of European Biochemical Soci eties.