Regulated Expression of a Complete Human β-Globin Gene Encoded by a Transmissible Retrovirus Vector

Abstract

We introduced a human beta-globin gene into murine erythroleukemia (MEL) cells by infection with recombinant retroviruses containing the complete genomic globin sequence. The beta-globin gene was correctly regulated during differentiation, steady-state mRNA levels being induced 5- to 30-fold after treatment of the cells with the chemical inducer dimethyl sulfoxide. Studies using vectors which yield integrated proviruses lacking transcriptional enhancer sequences indicated that neither retroviral transcription nor the retroviral enhancer sequences themselves had any obvious effect on expression of the globin gene. Viral RNA expression also appeared inducible, being considerably depressed in uninduced MEL cells but approaching normal wild-type levels after dimethyl sulfoxide treatment. We provide data which suggest that the control point for both repression and subsequent activation of virus expression in MEL cells lies in the viral enhancer element.

Induced Expression from the Moloney Murine Leukemia Virus Long Terminal Repeat during Differentiation of Human Myeloid Cells Is Mediated through Its Transcriptional Enhancer

“…While the Mo-MuLV LTR is expressed in some hematopoietic precursors, such as early erythroid cells and B and T lymphocytes (25,34), its activity appears to be depressed in pluripotent stem cells (6,10,14,20). The fact that the CAT activity in HL-60-derived cells stably carrying either the Mo-MuLV LTR or the SV40 promoter after induction of differentiation either to granulocytes with DMSO and HMBA or to monocytes and macrophages with sodium butyrate (SB) and PMA.…”