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This text discusses research on the Rift Valley fever virus, a zoonotic pathogen with a genome consisting of three segments. The focus is on the ambisense S segment, which contains exposed non-encapsidated RNA in the center overlapping with the intergenic region. This region is critical for optimal transcription and replication of the S segment, highlighting its functional importance. The study used iCLIP2 to map nucleoprotein interactions with viral RNAs and demonstrates the significance of this exposed RNA element in the virus's life cycle.
Rift Valley fever virus (RVFV) is a mosquito-borne zoonotic pathogen. Its RNA genome consists of two negative-sense segments (L and M) with one gene each, and one ambisense segment (S) with two opposing genes separated by the noncoding “intergenic region” (IGR). These vRNAs and the complementary cRNAs are encapsidated by nucleoprotein (N). Using iCLIP2 (individual-nucleotide resolution UV crosslinking and immunoprecipitation) to map all N-vRNA and N-cRNA interactions, we detect N coverage along the L and M segments. However, the S segment vRNA and cRNA each contain approximately 100 non-encapsidated nucleotides stretching from the IGR into the 5’-adjacent reading frame. These exposed regions are RNase-sensitive and predicted to form stem-loop structures with the mRNA transcription termination motif positioned near the top. Moreover, optimal S segment transcription and replication requires the entire exposed region rather than only the IGR. Thus, the RVFV S segment contains a central, non-encapsidated RNA region with a functional role.
Rift Valley fever virus (RVFV; genus Phlebovirus, family Phenuiviridae, order Bunyavirales) is a mosquito-borne zoonotic pathogen endemic in Africa. RVFV regularly causes small outbreaks, but occasionally also major and devastating epidemics leading to the death of thousands of cattle or sheep, and hundreds of humans<a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 1" title="McMillen, C. M. & Hartman A. L. Rift Valley fever: a threat to pregnant women hiding