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J. Virol., 09 1995, 5332-5336, Vol 69, No. 9
CZ Lee, PJ Chen and DS Chen
Hepatitis delta virus (HDV) encodes two proteins, the small delta antigen
(SHDAg) and large delta antigen (LHDAg). The latter is identical to the
former except for the presence of additional 19 amino acids at the C
terminus. While SHDAg is required for HDV replication, LHDAg inhibits
replication and, together with hepatitis B surface antigen (HBsAg), is
required for the assembly of HDV. The last 19 C- terminal amino acids of
LHDAg are essential for HDV assembly. Most of LHDAg (amino acids 19 to 146
and 163 to 195) had been shown to be dispensable for packaging with HBsAg.
To discern whether the last 19 C- terminal amino acids solely constitute
the signal for packaging with HBsAg, we constructed two LHDAg deletion
mutants and tested their abilities to be packaged with HBsAg in
cotransfection experiments. We found that deletion of amino acids 2 to 21
and 142 to 165 did not affect LHDAg packaging. This result suggested that
only the last 19 C- terminal amino acids of LHDAg are required for
packaging. We further constructed two plasmids which expressed c-H-ras with
or without additional 19 C-terminal amino acids identical to those in
LHDAg. Only c-H-ras with additional 19 amino acids could be cosecreted with
HBsAg in the cotransfection experiment. This result confirmed that the C-
terminal 19 amino acids are the packaging signal for HBsAg. We also tested
the trans activation activity and trans-dominant inhibitory activity of the
deletion mutants of SHDAg and LHDAg, respectively. In contrast to deletion
of amino acids 142 to 165, deletion of amino acids 2 to 21 impaired the
trans-dominant inhibitory activity of LHDAg. Deletion of amino acids 2 to
21 and 142 to 165 did not affect the trans activation activity of SHDAg.
This result suggested that a functional domain which is important for the
trans-dominant inhibitory activity of LHDAg exists in the amino terminus of
HDAg.
Copyright © 1995, American Society for Microbiology
Large hepatitis delta antigen in packaging and replication inhibition: role of the carboxyl-terminal 19 amino acids and amino-terminal sequences
Department of Internal Medicine, University Hospital, National Taiwan University, Taipei.
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