Previous Article | Next Article ![]()
Journal of Virology, March 1999, p. 2410-2419, Vol. 73, No. 3
Department of Microbiology, School of
Medicine, Meharry Medical College, Nashville, Tennessee 37208
Received 10 September 1998/Accepted 7 December 1998
Alphaviruses are mosquito-transmitted RNA viruses that cause
important diseases in both humans and livestock. Sindbis virus (SIN),
the type species of the alphavirus genus, carries a 11.7-kb positive-sense RNA genome which is capped at its 5' end and
polyadenylated at its 3' end. The 3' nontranslated region (3'NTR) of
the SIN genome carries many AU-rich motifs, including a 19-nucleotide (nt) conserved element (3'CSE) and a poly(A) tail. This 3'CSE and the
adjoining poly(A) tail are believed to regulate the synthesis of
negative-sense RNA and genome replication in vivo. We have recently
demonstrated that the SIN genome lacking the poly(A) tail was
infectious and that de novo polyadenylation could occur in vivo
(K. R. Hill, M. Hajjou, J. Hu, and R. Raju, J. Virol. 71:2693-2704, 1997). Here, we demonstrate that the 3'-terminal 29-nt
region of the SIN genome carries a signal for possible cytoplasmic polyadenylation. To further investigate the polyadenylation signals within the 3'NTR, we generated a battery of mutant genomes with mutations in the 3'NTR and tested their ability to generate infectious virus and undergo 3' polyadenylation in vivo. Engineered SIN genomes with terminal deletions within the 19-nt 3'CSE were infectious and
regained their poly(A) tail. Also, a SIN genome carrying the poly(A)
tail but lacking a part or the entire 19-nt 3'CSE was also infectious.
Sequence analysis of viruses generated from these engineered SIN
genomes demonstrated the addition of a variety of AU-rich sequence
motifs just adjacent to the poly(A) tail. The addition of AU-rich
motifs to the mutant SIN genomes appears to require the presence of a
significant portion of the 3'NTR. These results indicate the ability of
alphavirus RNAs to undergo 3' repair and the existence of a pathway for
the addition of AU-rich sequences and a poly(A) tail to their 3' end in
the infected host cell. Most importantly, these results indicate the
ability of alphavirus replication machinery to use a multitude of
AU-rich RNA sequences abutted by a poly(A) motif as promoters for
negative-sense RNA synthesis and genome replication in vivo. The
possible roles of cytoplasmic polyadenylation machinery, terminal
transferase-like enzymes, and the viral polymerase in the terminal
repair processes are discussed.
0022-538X/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
In Vivo Addition of Poly(A) Tail and AU-Rich
Sequences to the 3' Terminus of the Sindbis Virus RNA Genome: a
Novel 3'-End Repair Pathway
*
Corresponding author. Mailing address: Department of
Microbiology, Meharry Medical College, School of Medicine, 1005 D.B. Todd Blvd., Nashville, TN 37208. Phone: (615) 327 6687. Fax: (615) 327 6602. E-mail: ramasa25{at}ccvax.mmc.edu.
This article has been cited by other articles:
Copyright © 2009 by the American Society for Microbiology. For an alternate route to Journals.ASM.org, visit: http://intl-journals.asm.org | More Info»