Characterization of the promoter-directing expression of growth hormone ina monocyte cell line

Previous work from our laboratory has shown that cells of the immune system produce a growth hormone (GH) molecule similar to that produced by the pit uitary. in the present study, using Southern analysis of RT-PCR products an d sequencing of cloned cDNA molecules, we demonstrate that lymphoid cell li nes utilize the same promoter and first exon as the pituitary somatotrope. To identify the cis-elements involved in transcriptional regulation of immu ne cell-derived GH, we have coupled rat GH promoter fragments to a lucifera se reporter gene and transfected a monocyte cell line (P-388) by electropor ation. The results suggest the presence of both positive (299/-193 bp) and negative (-193/-107 bp) regulatory elements, The same constructs transfecte d in the pituitary cell line, GH3, in contrast to the monocyte cell line, s howed a gradual decrease in luciferase expression. The overexpression of GH F-1 or GHF-2 resulted in a modest but significant reduction in rat GH promo ter activity in the P-388 cell line. Taken together, the data suggest that immune cells utilize the same first exon and promoter sequence for the expr ession of monocyte GH as that reported for the expression of pituitary GH. Further, it appears that sequences between -299 and -107 bp are important i n the regulation of the promoter where different transcription factors may be recruited to promote GH expression in a monocyte cell line, Copyright (C ) 2000 S. Karger AG, Basel.