Structural basis for suppression of a host antiviral response by influenza A virus.
Influenza A viruses are responsible for seasonal epidemics and high mortality pandemics. A major function of the viral NS1A protein, a virulence factor, is the inhibition of the production of IFN-beta mRNA and other antiviral mRNAs. The NS1A protein of the human influenza A/Udorn/72 (Ud) virus inhibits the production of these antiviral mRNAs by binding the cellular 30-kDa subunit of the cleavage and polyadenylation specificity factor (CPSF30), which is required for the 3' end processing of all cellular pre-mRNAs. Here we report the 1.95-A resolution X-ray crystal structure of the complex formed between the second and third zinc finger domain (F2F3) of CPSF30 and the C-terminal domain of the Ud NS1A protein. The complex is a tetramer, in which each of two F2F3 molecules wraps around two NS1A effector domains that interact with each other head-to-head. This structure identifies a CPSF30 binding pocket on NS1A comprised of amino acid residues that are highly conserved among human influenza A viruses. Single amino acid changes within this binding pocket eliminate CPSF30 binding, and a recombinant Ud virus expressing an NS1A protein with such a substitution is attenuated and does not inhibit IFN-beta pre-mRNA processing. This binding pocket is a potential target for antiviral drug development. The crystal structure also reveals that two amino acids outside of this pocket, F103 and M106, which are highly conserved (>99%) among influenza A viruses isolated from humans, participate in key hydrophobic interactions with F2F3 that stabilize the complex.
Das
Kalyan
K
Center for Advanced Biotechnology and Medicine, Rutgers University, Piscataway, NJ 08854, USA.
Ma
Li-Chung
LC
Xiao
Rong
R
Radvansky
Brian
B
Aramini
James
J
Zhao
Li
L
Marklund
Jesper
J
Kuo
Rei-Lin
RL
Twu
Karen Y
KY
Arnold
Eddy
E
Krug
Robert M
RM
Montelione
Gaetano T
GT
D019943:Amino Acid Substitution; D001665:Binding Sites; D002460:Cell Line; D018360:Crystallography, X-Ray; D006801:Humans; D009980:Influenza A virus / Q000737:chemistry* / Q000276:immunology*; D050838:Interferon Regulatory Factor-3 / Q000378:metabolism; D008715:Methionine / Q000378:metabolism; D008958:Models, Molecular; D010649:Phenylalanine / Q000378:metabolism; D020836:Protein Structure, Quaternary; D017433:Protein Structure, Secondary; D013816:Thermodynamics; D017361:Viral Nonstructural Proteins / Q000737:chemistry / Q000378:metabolism; D016335:Zinc Fingers
D050838:Interferon Regulatory Factor-3; D017361:Viral Nonstructural Proteins; D010649:Phenylalanine; D008715:Methionine