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Mol. Cell. Biol., Sep 1996, 5004-5014, Vol 16, No. 9
D Fyodorov and E Deneris
In the PC12 neuroendocrine line, the neuronal nicotinic acetylcholine
receptor alpha3 gene promoter is activated by SCIP/Tst-1/Oct-6, a POU
domain transcription factor proposed to be important for regulating the
development of specific neural cell populations. In this study, we have
investigated the SCIP polypeptide domains involved in alpha3 promoter
activation. The characteristics of activation by a chimeric effector in
which the GAL4 DNA binding domain was substituted for the SCIP POU domain
were dramatically different from those of wild-type SCIP. At low effector
masses, the chimeric polypeptide weakly activated alpha3 in a GAL4
binding-site-dependent manner but then squelched transcription at higher
masses. In contrast, wild-type SCIP activation was not modulated by the
presence of multimerized SCIP binding sites, and squelching was not
observed. Analysis of wild-type SCIP truncations revealed that deletion of
the previously characterized SCIP amino-terminal activation domain did not
destroy activity of the factor. Surprisingly, a truncation expressing
nothing more than the POU domain was nearly as active as wild-type SCIP.
Moreover, cotransfection of a GAL4-VP16 effector with an effector
expressing just the SCIP POU domain resulted in synergistic activation of
the promoter. Synergistic activation did not depend on an Sp1 motif that is
the only functional alpha3 cis element outside the transcription start site
region. Our results show that the DNA binding domain of a POU factor is
capable of transcriptional activation probably through protein-protein
interactions with components of the basal transcription complex.
Copyright © 1996, American Society for Microbiology
The POU domain of SCIP/Tst-1/Oct-6 is sufficient for activation of any acetylcholine receptor promoter
Department of Neurosciences, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106, USA.
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