In vivo search for butyrate responsive sequences using transgenic mice carrying A gamma gene promoter mutants

We describe an in vivo approach, in transgenic mice, aimed to identify promoter elements responsible for the induction of gamma globin expression by butyrate. Transgenic lines carrying human A gamma gene promoter truncations at position -141, -201, -382, and -730 A gamma were treated with alpha amino butyric acid (alpha ABA), and effects on gamma globin expression were analyzed at the messenger RNA level. No induction of gamma gene expression was observed in animals carrying promoters truncated at positions -141, -201, or -382 A gamma, suggesting either that butyrate response elements (BRE) are not located in the proximal gamma gene promoter or, if they were, they require the cooperation of upstream sequences for gamma gene induction. Two animals from one line carrying the -730 A gamma truncation responded to alpha ABA treatment with significant increases in gamma gene expression, indicating that a BRE is located between position -382 and -730 region of the A gamma gene promoter. Because the maximum induction by alpha ABA is observed in transgenic mice carrying a A gamma gene promoter extending to nucleotide -1350, it is likely that another butyrate responsive element is located between -730 and -1350 of the A gamma gene promoter. These results indicate that the transgenic mouse model can be used for identification of DNA regions that contain cis elements involved in gamma globin gene inducibility.