Transient chloramphenicol acetyltransferase expression of the G gamma globin gene 5'-flanking regions containing substitutions of C----T at position -158, G----A at position -161, and T----A at position -175 in K562 cells.

The expression of G gamma is affected by mutations that occur in promoter sequences located in the 5'-flanking region of the gene. We have assayed the promoter activity of G gamma genes that have mutations of C----T at position -158 or G----A at position -161. In addition, we determined the activity of a promoter fragment containing T----A at position -175 (in the octamer motif) in combination with a -158 C----T which was produced during the polymerase chain reaction amplification procedure. Constructs containing these fragments were transfected by electroporation into K562 cells and the promoter activity was measured as chloramphenicol acetyltransferase activity. The data show a 4-5-fold enhancement of activity for the -158 C----T and the -161 G----A promoters over the 'normal' G gamma promoter and an 8-fold increase in the activity of the promoter with the double mutation (-158 C----T and -175 T----A). These results are consistent with data involving the increase in G gamma production in patients heterozygous for these mutations.