Dengue 2 virus NS2B and NS3 form a stable complex that can cleave NS3 within the helicase domain.
Flavivirus genomic RNA is translated into a large polyprotein that is processed into structural and nonstructural proteins. The N-termini of several nonstructural proteins are produced by cleavage at dibasic sites by a two-component viral proteinase consisting of NS2B and NS3. NS3 contains a trypsin-like serine proteinase domain at its N-terminus, whereas the function of NS2B in proteolysis is yet to be determined. We have used an NS3-specific antiserum, under nondenaturing conditions, to demonstrate that NS2B and NS3 form a complex both in vitro and in vivo. The N-terminal 184 residues of NS3 are sufficient to form the complex with NS2B. The complex forms efficiently when the NS2B and NS3 are translated from two different mRNAs as well as when NS2B and NS3 are translated as a polyprotein from the same mRNA. A chimeric complex can be formed between yellow fever NS2B and a chimeric yellow fever-dengue 2 NS3. Using anti-NS3 antisera, we also found that a 50-kDa fragment of NS3, consisting of the N-terminal approximately 460 residues, is produced in infected mammalian cells. This fragment is not produced in infected mosquito cells, but will form in Triton X-100 lysates of mosquito cells. The cleavage of NS3 to form this fragment is catalyzed by the NS3 proteinase itself and proteolysis requires NS2B. Examination of the amino acid sequence of NS3 reveals a potential conserved cleavage site that resembles other sites cleaved by the NS3/NS2B proteinase; this site occurs within a conserved RNA helicase sequence motif. The importance of this alternatively processed form of NS3 and its role in the replication cycle of dengue virus remain to be determined.
Arias
C F
CF
Division of Biology, California Institute of Technology, Pasadena 91125.
Preugschat
F
F
Strauss
J H
JH
D000330:Aedes; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D002999:Clone Cells; D006224:Cricetinae; D003716:Dengue Virus / Q000235:genetics / Q000378:metabolism*; D004355:Drug Stability; D007668:Kidney; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009838:Oligodeoxyribonucleotides; D016366:Open Reading Frames; D010449:Peptide Mapping; D014176:Protein Biosynthesis; D020365:RNA Helicases; D012316:RNA Nucleotidyltransferases / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D012697:Serine Endopeptidases / Q000235:genetics / Q000378:metabolism*; D017361:Viral Nonstructural Proteins / Q000235:genetics / Q000378:metabolism*; D043583:Nucleoside-Triphosphatase; D053487:DEAD-box RNA Helicases; D000085242:Viral Proteases
D009838:Oligodeoxyribonucleotides; D020365:RNA Helicases; D012316:RNA Nucleotidyltransferases; D012333:RNA, Messenger; D012697:Serine Endopeptidases; D017361:Viral Nonstructural Proteins; C080102:NS2B protein, flavivirus; C060028:NS3 protein, flavivirus; D043583:Nucleoside-Triphosphatase; D053487:DEAD-box RNA Helicases; D000085242:Viral Proteases