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Journal of Virology, July 2000, p. 6242-6250, Vol. 74, No. 14
Department of Microbiology and Immunology,
State University of New York Health Science Center at Brooklyn,
Brooklyn, New York 11203,1 and A.
N. Belozersky Institute of Physico-Chemical Biology, Moscow State
University, 119899 Moscow, Russia2
Received 14 December 1999/Accepted 20 April 2000
Hepatitis C virus translation is initiated on a ~330-nucleotide
(nt)-long internal ribosomal entry site (IRES) at the 5' end of the
genome. In this process, a 43S preinitiation complex (comprising a 40S
ribosomal subunit, eukaryotic initiation factor 3 (eIF3), and a ternary
[eIF2-GTP-initiator tRNA] complex) binds the IRES in a precise manner
so that the initiation codon is placed at the ribosomal P site. This
binding step involves specific interactions between the IRES and
different components of the 43S complex. The 40S subunit and eIF3 can
bind to the IRES independently; previous analyses revealed that eIF3
binds specifically to an apical half of IRES domain III. Nucleotides in
the IRES that are involved in the interaction with the 40S subunit were
identified by RNase footprinting and mapped to the basal half of domain
III and in domain IV. Interaction sites were identified in locations
that have been found to be essential for IRES function, including (i) the apical loop residues GGG266-268 in subdomain IIId and
(ii) the pseudoknot. Extensive protection from RNase cleavage also occurred downstream of the pseudoknot in domain IV, flanking both sides
of the initiation codon and corresponding in length to that of the
mRNA-binding cleft of the 40S subunit. These results indicate that the
40S subunit makes multiple interactions with the IRES and suggest that
only nucleotides in domain IV are inserted into the mRNA-binding cleft
of the 40S subunit.
0022-538X/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
An Enzymatic Footprinting Analysis of the
Interaction of 40S Ribosomal Subunits with the Internal Ribosomal Entry
Site of Hepatitis C Virus
*
Corresponding author. Mailing address: State University
of New York Health Science Center at Brooklyn, 450 Clarkson Ave., Brooklyn, NY 11203. Phone: (718) 270-1034. Fax: (718) 270-2656. E-mail:
chellen{at}netmail.hscbklyn.edu.
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