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Journal of Virology, September 2001, p. 8597-8604, Vol. 75, No. 18
Campus de Cantoblanco, Centro Nacional de
Biotecnología (CSIC), 28049 Madrid, Spain
Received 21 February 2001/Accepted 5 June 2001
The PA subunit of the influenza virus polymerase complex is a
phosphoprotein that induces proteolytic degradation of coexpressed proteins. Point mutants with reduced proteolysis induction reconstitute viral ribonucleoproteins defective in replication but not in
transcriptional activity. To look for cellular factors that could
associate with PA protein, we have carried out a yeast two-hybrid
screen. Using a human kidney cDNA library, we identified two different
interacting clones. One of them was identified as the human homologue
of a previously described cDNA clone from Gallus gallus
called CLE. The human gene encodes a protein of 36 kDa (hCLE) and is
expressed ubiquitously in all human organs tested. The interaction of
PA and hCLE was also observed with purified proteins in vitro by using
pull-down and pep-spot experiments. Mapping of the interaction showed
that hCLE interacts with PA subunit at two regions (positions 493 to
512 and 557 to 574) in the PA protein sequence. Immunofluorescence studies showed that the hCLE protein localizes in both the nucleus and
the cytosol, although with a predominantly cytosolic distribution. hCLE
was found associated with active, highly purified virus
ribonucleoproteins reconstituted in vivo from cloned cDNAs, suggesting
that PA-hCLE interaction is functionally relevant. Searches in the
databases showed that hCLE has 38% sequence homology to the central
region of the yeast factor Cdc68, which modulates transcription by
interaction with transactivators. Similar homologies were found with
the other members of the Cdc68 homologue family of transcriptional
activators, including the human FACT protein.
0022-538X/01/$04.00+0 DOI: 10.1128/JVI.75.18.8597-8604.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
PA Subunit from Influenza Virus Polymerase Complex
Interacts with a Cellular Protein with Homology to a Family of
Transcriptional Activators

*
Corresponding author. Mailing address: Centro Nacional
de Biotecnología (CSIC), Campus de Cantoblanco, 28049 Madrid,
Spain. Phone: 91 5854914. Fax: 91 5854506. E-mail:
anmartin{at}cnb.uam.es.
Present address: University of Dundee, Dundee DD1 5EH, United Kingdom.
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