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J. Virol., 09 1995, 5754-5762, Vol 69, No. 9
D Garcin, M Lezzi, M Dobbs, RM Elliott, C Schmaljohn, CY Kang and D Kolakofsky
We examined the 5' ends of Hantaan virus (HTN) genomes and mRNAs to gain
insight into the manner in which these chains were initiated. Like those of
all members of the family Bunyaviridae described so far, the HTN mRNAs
contained 5' terminal extensions that were heterogeneous in both length and
sequence, presumably because HTN also "cap snatches" host mRNAs to initiate
the viral mRNAs. Unexpectedly, however, almost all of the mRNAs contained a
G residue at position -1, and a large fraction also lacked precisely one of
the three UAG repeats at the termini. The genomes, on the other hand,
commenced with a U residue at position +1, but only 5' monophosphates were
found here, indicating that these chains may not have initiated with UTP at
this position. Taken together, these unusual findings suggest a
prime-and-realign mechanism of chain initiation in which mRNAs are
initiated with a G- terminated host cell primer and genomes with GTP, not
at the 3' end of the genome template but internally (opposite the template
C at position +3), and after extension by one or a few nucleotides, the
nascent chain realigns backwards by virtue of the terminal sequence
repeats, before processive elongation takes place. For genome initiation,
an endonuclease, perhaps that involved in cap snatching, is postulated to
remove the 5' terminal extension of the genome, leaving the 5' pU at
position +1.
Copyright © 1995, American Society for Microbiology
The 5' ends of Hantaan virus (Bunyaviridae) RNAs suggest a prime-and- realign mechanism for the initiation of RNA synthesis
Department of Genetics and Microbiology, University of Geneva School of Medicine, Switzerland.
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