Influence of capping and polyadenylation on mRNA expression and on antisense RNA mediated inhibition of gene expression

In order to investigate the influence of CAP and poly(A)-tail on mRNA expression and on antisense mediated inhibition of gene expression, coinjections of different expression vectors coding for Chloramphenicol-Acetyltransferase (CAT) sense- or antisense RNAs, respectively, were performed. Different in vitro transcribed and modified sense and antisense RNAs were injected into nucleus or cytoplasm of COS7-cells. It can be concluded that the combination of capping and polyadenylation ensures efficient gene expression and is required for transport of mRNA from the nucleus to the cytoplasm. In contrast, antisense experiments suggest that the length of antisense RNAs play an important role for the inhibitory capability of antisense molecules and expression reduction occurs independently of CAP and poly(A) tail. A model for intermolecular hybridization and suppression of gene expression based on the secondary structures of the CAT mRNA and its corresponding antisense RNA is presented.