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Journal of Virology, August 1999, p. 6533-6539, Vol. 73, No. 8
Fox Chase Cancer Center, Philadelphia,
Pennsylvania 19111-2497
Received 30 December 1998/Accepted 21 April 1999
The genome of hepatitis delta virus (HDV) is a 1,679-nucleotide
(nt) single-stranded circular RNA that is predicted to fold into an
unbranched rodlike structure. During replication, two complementary
RNAs are also detected: an exact complement, referred to as the
antigenome, and an 800-nt polyadenylated RNA that could act as the mRNA
for the delta antigen. We used a 5' rapid amplification of cDNA ends
procedure, followed by cloning and sequencing, to determine the 5' ends
of the polyadenylated RNAs produced during HDV genome replication
following initiation under different experimental conditions. The
analyzed RNAs were from the liver of an infected woodchuck and from a
liver cell line at 6 days after transfection with either an HDV cDNA or
ribonucleoprotein (RNP) complexes assembled in vitro with HDV genomic
RNA and purified recombinant small delta protein. In all three
situations the 5' ends mapped specifically to nt 1630. In relationship
to what is called the top end of the unbranched rodlike structure
predicted for the genomic RNA template, this site is located 10 nt from
the top, and in the middle of a 3-nt external bulge. Following
transfection with RNP, such specific 5' ends could be detected as early
as 24 h. We next constructed a series of mutants of this predicted
bulge region and of an adjacent 6-bp stem and the top 5-nt loop. Some
of these mutations decreased the ability of the genome to undergo
antigenomic RNA synthesis and accumulation and/or altered the location
of the detected 5' ends. The observed end located at nt 1630, and most
of the novel 5' ends, were consistent with transcription initiation
events that preferentially used a purine. The present studies do not prove that the detected 5' ends correspond to initiation sites and do
not establish the hypothesis that there is a promoter element in the
vicinity, but they do show that the location of the observed 5' ends
could be controlled by nucleotide sequences at and around nt 1630.
0022-538X/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Characterization of the 5' Ends for Polyadenylated
RNAs Synthesized during the Replication of Hepatitis Delta
Virus
*
Corresponding author. Mailing address: Fox Chase Cancer
Center, 7701 Burholme Ave., Philadelphia, PA 19111-2497. Phone: (215) 728-2436. Fax: (215) 728-3616. E-mail:
JM_Taylor{at}FCCC.edu.
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