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J. Biol. Chem., Vol. 266, Issue 13, 8416-8425, 05, 1991
M Hatzoglou, F Bosch, EA Park and RW Hanson
The interaction of promoters contained in a Moloney murine leukemia virus
(MoMLV)-based retroviral vector was studied after infection of FTO-2B rat
hepatoma and NIH 3T3 mouse fibroblast cells. Segments of the
phosphoenolpyruvate carboxykinase (PEPCK) promoter-regulatory region, which
are known from previous studies to confer responsiveness to hormones, were
linked to the structural genes for bovine growth hormone, amino-3'-glycosyl
phosphotransferase (neo), and herpes-virus thymidine kinase and inserted
into a MoMLV-based retroviral vector. In vectors in which PEPCK was the
only internal promoter, it was the major site of gene transcription. This
dominant effect was independent of the orientation of the PEPCK promoter
relative to the 5' long terminal repeat of the provirus and was noted with
as little as -174 base pairs of the 5'-flanking sequence. NIH 3T3 cells,
which do not express the endogenous PEPCK gene, transcribed the transduced
PEPCK-chimeric genes at the same high levels as was observed in hepatoma
cells. When two promoters were present in the provirus, the expression of
chimeric structural genes depended on the relative position and orientation
of these genes as well as the type of cell infected by the retrovirus.
Differential responses of proviral promoters in infected cells were also
observed in the presence of hormones. Dibutyryl cyclic AMP increased the
expression of genes linked to the PEPCK promoter in FTO- 2B and NIH 3T3
cells, whereas glucocorticoids stimulated transcription from both the PEPCK
promoter and the long terminal repeat in FTO-2B cells. The effect of these
hormones on transcription of proviral promoters depended on their position
relative to the 5' long terminal repeat. In contrast, insulin uniformly
inhibited transcription from the PEPCK promoter in a position-independent
manner but only in hepatoma cells and not in fibroblasts. In clonally
isolated FTO-2B cells infected with a retrovirus, the site of proviral
integration was also a major factor determining the expression and hormonal
regulation from the internal promoters. The data suggest that the hormonal
regulation of the expression of genes contained in retroviral vectors
depends on the type and position of the regulatory elements present in the
provirus and the lineage of the infected cell.
Hormonal control of interacting promoters introduced into cells by retroviruses
Pew Center for Molecular Nutrition, Case Western Reserve University, School of Medicine, Cleveland, Ohio 44106.
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