Circular and Linear Conformations of the Dengue Virus Genome Are

SERGIO VILLORDO, DIEGO ALVAREZ, CLAUDIA FILOMATORI, AND ANDREA GAMARNIK

MADRID, SPAIN

Workshop; REPLICATION AND RECOMBINATION OF RNA VIRUS, Madrid, Spain; 2009

SPONSORED BY JUAN MARCH FOUNDATION

Circular and Linear Conformations of the Dengue Virus Genome Are Necessary for Viral RNA Amplification / Sergio Villordo, Diego Alvarez, Claudia Filomatori, and Andrea Gamarnik Fundación Instituto Leloir, Buenos Aires, Argentina Dengue virus is an important human pathogen transmitted by mosquitoes that belongs to the Flaviviridae family. The viral genome is a single stranded RNA molecule of positive polarity. Viral RNA synthesis is catalyzed by the NS5 RNA dependent RNA polymerase (RdRp) and involves the NS3 helicase together with other cellular and viral factors. We have previously identified an RNA structure present at the 5’ end of the genome (named SLA) that binds the polymerase and promotes viral RNA synthesis. This SLA functions co-ordinately with two pairs of complementary sequences that mediate long range RNA-RNA interactions. In the proposed model, genome cyclization facilitates the initiation of RNA synthesis by locating the RdRp (bound to the 5’SLA) near the 3’ end initiation site. We also identified different RNA sequences and structures at the viral 5’ and 3’ UTRs that modulate the activity of the promoter SLA in vivo and in vitro. More recently, we became interested in the role of the equilibrium between the linear and circular conformation of the viral RNA during dengue virus replication. Incorporation of mutations in dengue virus infectious clones that increase the stability of the circular or the linear forms of the RNA resulted in spontaneous mutations that restored the wild type stability of the long-range RNA-RNA interaction. We also defined conserved RNA structures as in vivo sensors of the linear conformation of the genome that were essential for viral replication.  We conclude that the dengue virus genome is dynamic and both linear and circular conformations are necessary for RNA amplification.