How does the journey affect the message(RNA)?

Research has determined that different RNAs within the cell (mRNA, snRNA, rRNA, tRNA) use distinct pathways to facilitate their movement from the nucleus to the cytoplasm. But does the nature of the pathway used affect the metabolism of the RNA? Recent studies have begun to address this question by examining the regulation of similar mRNAs exported by different pathways. We summarize the observations from several groups indicating that, in the case of HIV-1 mRNAs, the export pathway has dramatic effects on sensitivity to a translational inhibitor as well as the fate of the encoded proteins. Given that the mRNAs do not differ in physical structure (5' cap, 3' poly A tail), these findings suggest that the export pathway generates a distinct RNP composition that dictates the fate of the mRNA. Recent results have begun to define the composition of the HIV-1 RNP and, in turn, further re-enforced the hypothesis that these viral mRNAs have very distinct fates in the cytoplasm.