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lunes, 8 de febrero de 2010

Expression Strategies of Ambisense Viruses

Among the negative RNA viruses, ambisense RNA viruses occupy a distinct niche. Ambisense viruses contain at least one ambisense RNA segment, i.e. an RNA that is in part of positive and in part of negative polarity. Because of this unique gene organization, one might expect ambisense RNA viruses to borrow expression strategies from both positive and negative RNA viruses. However, they have little in common with positive RNA viruses, but possess many features of negative RNA viruses. Transcription and/or replication of their RNAs appear generally to be coupled to translation. Such coupling might be important to ensure temporal control of gene expression, allowing the two genes of an ambisense RNA segment to be differently regulated. Ambisense viruses can infect one host asymptomatically and in certain cases, they can lethally infect two hosts of a different kingdom. A possible model to explain the differential behavior of a given virus in different hosts could be that perturbation of the translation machinery would lead to differences in the severity of symptoms.

The ambisense coding strategy is an unusual way of encoding genes that presumably allows the virus to temporally control expression of the viral proteins, in particular if coupling of translation to transcription enhances the level of vc-encoded versus v-encoded protein expression. In any event, translation itself and/or translational control appear to play an important role in regulation of gene expression of ambisense viruses. Ambisense viruses have two hosts in which they can replicate. In their vector or reservoir host, infection is usually asymptomatic. However, in another host, multiplication of the virus can be lethal. Replication/transcription experiments in different host cell types would be helpful to shed further light on the differences observed in different hosts. At present, there are many complementary ways to study ambisense virus replication/ transcription such as cell culture, in vitro assays and reverse genetics systems. Since ambisense viruses are the meeting point of different viral families and are able to replicate in different hosts whether plants or animals and have different behaviors depending on the host, it would be particularly important to better understand the complex replicative cycle of ambisense viruses, in order to find the means to alleviate the lethal aspects of these pathogens.

Expression strategies of ambisense viruses. Virus Research 93: 141-150, 2003. doi: 10.1016/S0168-1702(03)00094-7

Taken by: AJCann, Expression strategies of ambisense viruses, (on line) url: (cited on) Feb 8/2010

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