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Journal of Virology, June 2000, p. 5509-5515, Vol. 74, No. 12
Fox Chase Cancer Center, Philadelphia,
Pennsylvania 19111-2497,1 and
Harvard Medical School, Boston, Massachusetts
021152
Received 15 December 1999/Accepted 9 March 2000
The 195- and 214-amino-acid (aa) forms of the delta protein
(
0022-538X/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Interactions between Hepatitis Delta Virus
Proteins
Ag-S and
Ag-L, respectively) of hepatitis delta virus (HDV) differ only in the 19-aa C-terminal extension unique to
Ag-L.
Ag-S is needed for genome replication, while
Ag-L is needed for
particle assembly. These proteins share a region at aa 12 to 60, which
mediates protein-protein interactions essential for HDV replication. H. Zuccola et al. (Structure 6:821-830, 1998) reported a crystal
structure for a peptide spanning this region which demonstrates an
antiparallel coiled-coil dimer interaction with the potential
to form tetramers of dimers. Our studies tested whether predictions
based on this structure could be extrapolated to conditions where the
peptide was replaced by full-length
Ag-S or
Ag-L, and when the
assays were not in vitro but in vivo. Nine amino acids that are
conserved between several isolates of HDV and predicted to be important
in multimerization were mutated to alanine on both
Ag-S and
Ag-L.
We found that the predicted hierarchy of importance of these nine
mutations correlated to a significant extent with the observed in vivo
effects on the ability of these proteins to (i) support in
trans the replication of the HDV genome when expressed on
Ag-S and (ii) act as dominant-negative inhibitors of
replication when expressed on
Ag-L. We thus infer that these
biological activities of
Ag depend on ordered protein-protein interactions.
*
Corresponding author. Mailing address: Fox Chase Cancer
Center, 7701 Burholme Ave., Philadelphia, PA 19111-2497. Phone: (215) 728-2436. Fax: (215) 728-3105. E-mail:
jm_taylor{at}fccc.edu.
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