Regulation of murine alpha-, beta major-, and beta minor-globin gene expression.

Transcriptional properties of the mouse globin genes and their promoters were examined in COS cells using transient expression assays. Transfected intact mouse alpha 1-globin genes generate transcripts, whereas beta maj and beta min globin transcripts are detected only if the genes are associated with a strong exogenous (SV40) enhancer sequence. Under these conditions the ratio of accumulated beta maj and beta min mRNA sequences approximates the 4:1 ratio observed in reticulocytes and murine erythroleukemia cells (MELC) induced to differentiate by hexamethylene bisacetamide (HMBA). As determined using hybrid genes consisting of globin gene 5' regions fused to the chloramphenicol acetyltransferase (CAT) structural gene, this 4:1 ratio appears dependent upon the relative activities of the two 5' promoter regions.