Predominant expression of human Agamma--in contrast with beta-globin gene in MEL cells transfected with the construct muLCRAgamma psibeta deltabeta.

A cosmid construct muLCRAgamma psibeta deltabeta were induced into mouse erythroleukemia cell lines 585 that expresses murine adult globin only and MEL GM-979 that expresses both murine embryonic and adult globins. Similar patterns of human globin gene expression were displayed in the two MEL cell lines transfected with the construct. Inducible expression of the Agamma- and beta-gene was observed during induced cell differentiation. However, the expression level of the Agamma-globin gene is much higher than that of the beta-globin gene in either uninduced or induced MEL transformants. No gamma to beta switching happened in the stable MEL transformants following a continuous culture. The much more effective enhance of the muLCR on the Agamma-globin gene than that on the beta-globin gene is resulted probably from the fact that the distance between the LCR and the beta-globin gene is much longer than that between the LCR and the Agamma-globin gene in the construct, in comparison with other constructs containing HS2 or muLCR linked to both of gamma- and beta-globin genes in different order. Two suggestions can be derived from these results: 1) A competition between the gamma- and beta-globin gene for interaction with the LCR may indeed present, but only an enough long distance difference between the LCR to the gamma- and to the beta-gene can effectively influence the competition; 2) Unlike transgenic mice, MEL cells are incapable of reconstructing the regulatory information involved in developmental control when it is provided by a fragment of the beta-globin gene cluster with limited length.