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J Virol, April 1998, p. 2896-2904, Vol. 72, No. 4
Department of Biochemistry and Molecular
Genetics, Schools of Medicine and Dentistry, University of Alabama
at Birmingham, Birmingham, Alabama 35294-0005
Received 20 August 1997/Accepted 18 December 1997
Adenovirus (Ad) replicative complexes form at discrete sites on the
nuclear matrix (NM) via an interaction mediated by the precursor of the
terminal protein (pTP). The identities of cellular proteins involved in
these complexes have remained obscure. We present evidence that pTP
binds to a multifunctional pyrimidine biosynthesis enzyme found at
replication domains on the NM. Far-Western blotting identified proteins
of 150 and 240 kDa that had pTP binding activity. Amino acid sequencing
of the 150-kDa band revealed sequence identity to carbamyl phosphate
synthetase I (CPS I) and a high degree of homology to the related
trifunctional enzyme known as CAD (for carbamyl phosphate synthetase,
aspartate transcarbamylase, and dihydroorotase). Western blotting with
an antibody directed against CAD detected a 240-kDa band that
comigrated with that detected by pTP far-Western blotting. Binding
experiments showed that a pTP-CAD complex was immunoprecipitable from
cell extracts in which pTP was expressed by a vaccinia virus
recombinant. Additionally, in vitro-translated epitope-tagged pTP and
CAD were immunoprecipitable as a complex, indicating the occurrence of
a protein-protein interaction. Confocal fluorescence microscopy of
Ad-infected NM showed that pTP and CAD colocalized in nuclear foci.
Both pTP and CAD were confirmed to colocalize with active sites of
replication detected by bromodeoxyuridine incorporation. These data
support the concept that the pTP-CAD interaction may allow anchorage of
Ad replication complexes in the proximity of required cellular factors
and may help to segregate replicated and unreplicated viral DNA.
0022-538X/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Adenovirus Preterminal Protein Binds to the CAD
Enzyme at Active Sites of Viral DNA Replication on the Nuclear
Matrix
*
Corresponding author. Mailing address: Department of
Biochemistry and Molecular Genetics, Room 460, Basic Health Sciences Building, University of Alabama at Birmingham, Birmingham, AL 35294-0005. Phone: (205) 934-4734. Fax: (205) 934-0758. E-mail: Jengler{at}bmg.bhs.uab.edu.
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