In vivo search for butyrate responsive sequences using transgenic mice carrying (A)γ gene promoter mutants

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