| During rotavirus replication, there is transcriptional and translational control of rotavirus gene expression; however, the molecular mechanisms that regulate expression of each the rotavirus genes are not well defined. Therefore, we are investigating the mechanisms of regulation of rotavirus gene expression and the possible involvement of nonstructural protein NSP1. The identification of a potential mechanism for the regulation of rotavirus gene expression was evaluated using two viral genes that are expressed at different levels early in the infection. VP6, encoded by gene segment 6, is expressed in excess over NSP1, which is encoded by gene segment 5. The mRNA levels of the two genes were measured and no significant difference was found. The half-life of the two proteins was calculated to be the same, indicating that the stability of NSP1 and VP6 are similar. Polysome analyses demonstrated that gene 6 mRNA is translated more efficiently than gene 5 mRNA, and further studies of gene 5 illustrated that gene 5 mRNA is a poor template for initiating translation. Therefore, one mechanism responsible for the difference in the levels of expression of gene 5 mRNA and gene 6 mRNA occurs at the level of translation initiation.;To investigate the role of NSP1 in regulating viral gene expression, the sedimentation of rotavirus mRNAs in polyribosome gradients were compared between a mutant viral strain lacking NSP1 and a wildtype strain. Gene 6 mRNA showed no difference in sedimentation at four and six hours post infection. However, when the sedimentation of gene 6 at two hours post infection was examined, a greater percentage of gene 6 mRNA of the mutant strain sedimented in the polysomal fractions compared to wildtype gene 6 mRNA. Gene 11 mRNA showed little difference in the sedimentation at two hours post infection, but at 4 and 6 hours post-infection, a greater percentage of gene 11 mRNA sedimented in the polysome fractions for the mutant strain compared to the wildtype strain. These data suggest that rotavirus genes are differentially regulated and that NSP1 may participate in the regulation of viral gene expression. |
