home
***
CD-ROM
|
disk
|
FTP
|
other
***
search
/
Shareware Overload Trio 2
/
Shareware Overload Trio Volume 2 (Chestnut CD-ROM).ISO
/
dir26
/
med9408c.zip
/
M9480497.TXT
< prev
next >
Wrap
Text File
|
1994-08-20
|
4KB
|
53 lines
Document 0497
DOCN M9480497
TI Selected mutations of the duck hepatitis B virus P gene RNase H domain
affect both RNA packaging and priming of minus-strand DNA synthesis.
DT 9410
AU Chen Y; Robinson WS; Marion PL; Department of Medicine, Stanford
University School of Medicine,; California 94305.
SO J Virol. 1994 Aug;68(8):5232-8. Unique Identifier : AIDSLINE
MED/94309190
AB The genome of all hepadnaviruses has an open reading frame called the P
gene, which encodes a polypeptide of 90 to 97 kDa. The product or
products of this P gene are involved in multiple functions of the viral
life cycle. These functions include a priming activity which initiates
minus-strand DNA synthesis, a polymerase activity which synthesizes DNA
by using either RNA or DNA templates (reverse transcriptase), a nuclease
activity which degrades the RNA strand of RNA-DNA hybrids (RNase H), and
involvement in packaging the RNA pregenome into nucleocapsids. In a
previous study, we found that a single point mutation at position 711 in
the duck hepatitis B virus (DHBV) P gene product RNase H domain
prevented viral RNA packaging. In the present experiments, we have
mutated additional conserved amino acids in the DHBV RNase H domain and
examined the ability of viral genomes containing these mutations to
package RNA and replicate viral DNA. Charged and sulfur group amino
acids adjacent to Cys-711 were mutated. None of these mutants was
defective in either RNA packaging or viral replication. We also tested a
number of mutations on the basis of common elements in the crystal
structures of Escherichia coli and human immunodeficiency virus reverse
transcriptase RNase H enzymes and on the basis of the similarities of
their amino acid sequences to those of the RNase H domains of DHBV and
HBV. Our results revealed that the entire beta 4 strand and amino acids
Leu-712, Leu-697, and Val-719 in the putative hydrophobic cores of the
beta 4, alpha A, and alpha B regions, respectively, are involved in
pregenomic RNA encapsidation. This suggests that the basic structure of
the RNase H domain in the DHBV P gene product is required for viral RNA
packaging. We used the in vitro DHBV minus-strand DNA priming system
developed by Wang and Seeger (G.-H. Wang and C. Seeger, Cell 71:663-670,
1992) to test the effect of RNase H packaging mutations on P gene
product enzymatic activity. While all packaging-defective mutants tested
maintained DNA priming activity, levels were decreased 5- to 20-fold
compared with that of the wild-type genome. This observation suggests
that the hepadnavirus RNase H domain plays a role in optimizing priming
of minus-strand DNA synthesis.
DE Amino Acid Sequence DNA Primers DNA, Viral/*BIOSYNTHESIS
Electrochemistry Hepatitis B Virus, Duck/ENZYMOLOGY/*GENETICS
Molecular Sequence Data Point Mutation Ribonuclease H, Calf
Thymus/*GENETICS/METABOLISM RNA Processing, Post-Transcriptional RNA,
Viral/*METABOLISM Support, U.S. Gov't, P.H.S. Viral
Proteins/*GENETICS/METABOLISM Virus Replication JOURNAL ARTICLE
SOURCE: National Library of Medicine. NOTICE: This material may be
protected by Copyright Law (Title 17, U.S.Code).