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Mol. Cell. Biol., Oct 1995, 5552-5562, Vol 15, No. 10
E Roulet, MT Armentero, G Krey, B Corthesy, C Dreyer, N Mermod and W Wahli
The nuclear factor I (NFI) family consists of sequence-specific DNA-
binding proteins that activate both transcription and adenovirus DNA
replication. We have characterized three new members of the NFI family that
belong to the Xenopus laevis NFI-X subtype and differ in their C- termini.
We show that these polypeptides can activate transcription in HeLa and
Drosophila Schneider line 2 cells, using an activation domain that is
subdivided into adjacent variable and subtype-specific domains each having
independent activation properties in chimeric proteins. Together, these two
domains constitute the full NFI-X transactivation potential. In addition,
we find that the X. laevis NFI-X proteins are capable of activating
adenovirus DNA replication through their conserved N-terminal DNA-binding
domains. Surprisingly, their in vitro DNA-binding activities are
specifically inhibited by a novel repressor domain contained within the
C-terminal part, while the dimerization and replication functions per se
are not affected. However, inhibition of DNA-binding activity in vitro is
relieved within the cell, as transcriptional activation occurs irrespective
of the presence of the repressor domain. Moreover, the region comprising
the repressor domain participates in transactivation. Mechanisms that may
allow the relief of DNA-binding inhibition in vivo and trigger
transcriptional activation are discussed.
Copyright © 1995, American Society for Microbiology
Regulation of the DNA-binding and transcriptional activities of Xenopus laevis NFI-X by a novel C-terminal domain
Institut de Biologie Animale, Universite de Lausanne, Switzerland.
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