Molecular and Cellular Biology, May 2001, p. 3482-3490, Vol. 21, No. 10
0270-7306/01/$04.00+0 DOI: 10.1128/MCB.21.10.3482-3490.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
B
Is
Required for Maximal Activation of NF-
B-Dependent
Transcription
Institute of Biomolecular Sciences, School of Biology, University of St. Andrews, The North Haugh, St. Andrews, KY16 9ST, Scotland,1 and Institut Jacques Monod, UMR 7592, 75251 Paris Cedex 05, France2
Received 30 October 2000/Returned for modification 13 November 2000/Accepted 20 February 2001
Transcriptional activation of NF-
B is mediated by signal-induced
phosphorylation and degradation of its inhibitor, I
B
. NF-
B
activation induces a rapid resynthesis of I
B
which is responsible
for postinduction repression of transcription. Following resynthesis,
I
B
translocates to the nucleus, removes template bound NF-
B,
and exports NF-
B to the cytoplasm in a transcriptionally inactive
form. Here we demonstrate that I
B
interacts directly with another
nucleocytoplasmic shuttling protein, hnRNPA1, both in vivo and in
vitro. This interaction requires one of the N-terminal RNA binding
domains of hnRNPA1 and the C-terminal region of I
B
. Cells lacking
hnRNPA1 are defective in NF-
B-dependent transcriptional activation,
but the defect in these cells is complemented by ectopic expression of
hnRNPA1. hnRNPA1 expression in these cells increased the amount of
I
B
degradation, compared to that of the control cells, in
response to activation by Epstein-Barr virus latent membrane protein 1. Thus in addition to regulating mRNA processing and transport, hnRNPA1
also contributes to the control of NF-
B-dependent transcription.
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