RNA dimerization plays a role in ribosomal frameshifting of the SARS coronavirus

Ishimaru, Daniella; Plant, Ewan P.; Sims, Amy C.; Yount, Boyd L.; Roth, Braden M.; Eldho, Nadukkudy V.; Pérez-Alvarado, Gabriela C.; Armbruster, David W.; Baric, Ralph S.; Dinman, Jonathan D.; Taylor, Deborah R.; Hennig, Mirko

Intermolecular loop-loop kissing of retroviral gRNA are initially metastable and subsequently converted to more stable mature duplexes catalysed by nucleocapsid proteins. Such processes involving palindromic 6-nt sequences have been extensively studied and described for Moloney murine leukemia virus (35), Hepatitis C virus (36) and Human immunodeficiency virus (HIV) dimers (15) . We thus asked the question whether S3L2 loop-loop kissing complexes ( Figure 5B ) can potentially form extended duplexes ( Figure 5C ). Seminal work by Laughrea and Jette´have established that loose (loop-loop kissing) dimers are unstable when subjected to native electrophoresis at 25 C, while tight (extended) duplexes resist these conditions (37, 38) . As shown in lane 1 of Figures 3A and B , S3L2 dimers, while detectable at 4 C, are not favored at 25 C, suggesting the formation of loop-loop kissing complexes.