Influenza virus non-structural protein NS1 cooperatively binds virus-specific (+)-strand RNA sequences
Soubieux, Denis
Non-structural protein NS1 of influenza viruses plays a major role in countering the interferon response of the host, and is involved in the metabolism of viral and cellular RNAs. Its multiple activities all require a functional RNA-binding domain. NS1 is generally thought to bind non-specifically to several viral and cellular RNAs, notably to double-stranded RNAs (dsRNAs). We asked whether NS1 could exhibit some sequence-specificity towards its RNA ligands, and performed an in vitro selection (SELEX) to isolate NS1-specific aptamers. We identified two virus-specific sequences that are characteristic of the viral RNAs of positive polarity. The first motif, AGCAAAAG, is strictly conserved at the 5’-end of all (+)-strand RNAs of influenzaviruses A. The second motif, UGAUUGAAG, is highly conserved in NS1-mRNA, 15 nucleotides downstream of NS1’s stop codon. In addition, most of NS1-aptamers had one or two symmetrically positioned copies of the 5’-GUAAC / 3’-CUUAG double-stranded motif, which closely resembles the canonical 5’-splice site. We characterized the interaction of NS1 with its RNA-aptamers and showed that NS1’s RNA-binding domain specifically recognizes both the sequence and structure of the virus-specific RNA-sequences. Cooperative binding of NS1’s RNA-binding domain leads to its oligomerization on the bound RNA. This strong and intimate interaction suggests that NS1 activity towards viral RNAs is much more specific than previously thought.
Показать больше [+] Меньше [-]