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Mol. Cell. Biol., Jan 1998, 110-121, Vol 18, No. 1
JM Li, X Shen, PP Hu and XF Wang
Transforming growth factor beta (TGF-beta) is the prototype of a large
superfamily of signaling molecules involved in the regulation of cell
growth and differentiation. In certain patients infected with human
immunodeficiency virus type 1 (HIV-1), increased levels of TGF-beta
promoted the production of virus and also impaired the host immune system.
In an effort to understand the signaling events linking TGF- beta action
and HIV production, we show here that TGF-beta can stimulate transcription
from the HIV-1 long terminal repeat (LTR) promoter through NF-kappaB
binding sites in both HaCaT and 300.19 pre-B cells. When introduced into a
minimal promoter, NF-kappaB binding sites supported nearly 30-fold
activation from the luciferase reporter upon TGF-beta treatment.
Electrophoretic mobility shift assay indicated that a major factor binding
to the NF-kappaB site is the p50-p65 heterodimeric NF-kappaB in HaCaT
cells. Coexpression of Gal4-p65 chimeric proteins supported TGF-beta
ligand-dependent gene expression from a luciferase reporter gene driven by
Gal4 DNA binding sites. NF- kappaB activity present in HaCaT cells was not
affected by TGF-beta treatment as judged by the unchanged DNA binding
activity and concentrations of p50 and p65 proteins. Consistently,
steady-state levels of IkappaB alpha and IkappaB beta proteins were not
changed by TGF-beta treatment. Our results demonstrate that TGF-beta is
able to stimulate transcription from the HIV-1 LTR promoter by activating
NF- kappaB through a mechanism distinct from the classic NF-kappaB
activation mechanism involving the degradation of IkappaB proteins.
Copyright © 1998, American Society for Microbiology
Transforming growth factor beta stimulates the human immunodeficiency virus 1 enhancer and requires NF-kappaB activity
Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, North Carolina 27708, USA.
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