The emergence of human noroviruses (NoV) as significant human pathogens over the last decades has highlighted the need to research and understand the replication and pathogenesis of this group of viruses. One of the major hurdles faced by researchers in this field has been the lack of a viable tissue culture system or small animal model with which to study human NoV replication. The discovery of a murine NoV in 2003 and the identification of its tropism for macrophage and dendritic cell lines has provided the opportunity to study aspects of NoV replication and pathogenesis that were previously closed to researchers.
Expression of human t‐cell leukemia virus type I (HTLV‐I) enzymes requires two ‐1 programmed ribosomal frameshifts. These events occur between the gag‐pro and pro‐pol open reading frames. Each frameshift site includes a heptanucleotide slippery sequence followed by a downstream structure, which act in cis to produce specific frameshift efficiencies. While ‐1 PRF and the slippery sequences of these frameshift sites have been established in HTLV‐I, their frameshift efficiencies and the structures within these sites have not been determined. In pro‐pol frameshift site, an RNA pseudoknot is predicted to fold downstream of the UUUAAAC slippery sequence. However, no structural data exist for this RNA. Here, we report a preliminary structure of the HTLV‐1 pro‐pol frameshift site RNA. Nucleotide reactivity data acquired from selective 2′‐hydroxyl acylation experiments analyzed by primer extension and thermodynamics‐based secondary structure predictions are consistent with a pseudoknot secondary structure. Additionally, non‐denaturing PAGE analysis of the wild‐type structure and two mutant RNAs confirmed that the fold of the wild‐type RNA is significantly different from RNAs of identical length that cannot form a pseudoknot structure. These results establish the existence of a pseudoknot structure in the HTLV‐1 pro‐pol frameshift site.
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