IMPAIRED ERYTHROID-SPECIFIC GENE-EXPRESSION IN CAMP-DEPENDENT PROTEINKINASE-DEFICIENT MURINE ERYTHROLEUKEMIA-CELLS

Murine erythroleukemia cells rendered deficient in cAMP-dependent prot ein kinase (A-kinase) activity by gene transfection are severely impai red in hexamethylene bisacetamide (HMBA)-induced differentiation (Pilz , R. B., Eigenthaler, M., and Boss, G. R. (1992) J. Biol. Chem. 267,16 161-16167). We now demonstrate that the A-kinase-deficient cells produ ce hemoglobin normally in response to exogenous hemin and that the hem e precursor delta-aminolevulinate (delta-ALA) significantly increases HMBA-induced synthesis of heme and globin chains in these cells; these data suggest that impaired heme synthesis is at least partially respo nsible for the cells' deficient hemoglobin synthesis. HMBA-induced exp ression of the erythroid-specific delta-ALA synthetase, porphobilinoge n deaminase, and beta-globin mRNAs was less in A-kinase-deficient cell s than in parental cells and was reduced in proportion to the cells' r esidual A-kinase activity; relative transcription rates of these genes were reduced concordantly. Impaired expression of these three erythro id-specific genes was a feature of many independently-derived A-kinase -deficient clones, and normal expression was found in transfectants wi th normal A-kinase activity. The A-kinase-deficient cells did not exhi bit a generalized defect in gene regulation since mRNA expression and transcription rates of H- and L-ferritin, c-myc, c-myb, and several ho usekeeping enzymes were similar in HMBA-treated parental and A-kinase- deficient cells. Our data suggest that A-kinase may be involved in reg ulating genes with erythroid-specific promoters and provide further ev idence for heme as a regulator of globin chain synthesis.