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Inhibition of apoptosis and NF- kappa B activation by vaccinia protein N1 occur via distinct binding surfaces and make different contributions to virulence

DOI: 10.1371/journal.ppat.1002430 DOI Help
PMID: 22194685 PMID Help

Authors: Carlos Maluquer De Motes (Imperial College London) , Samantha Cooray (Imperial College London) , Hongwei Ren (Imperial College London) , Gabriel M. F. Almeida (Imperial College London) , Kieran Mcgourty (Imperial College London) , Mohammad W. Bahar (Wellcome Trust Centre for Human Genetics, University of Oxford) , David I. Stuart (Wellcome Trust Centre for Human Genetics, University of Oxford; Diamond Light Source) , Jonathan M. Grimes (Wellcome Trust Centre for Human Genetics, University of Oxford; Diamond Light Source) , Stephen C. Graham (University of Cambridge) , Geoffrey L. Smith (Imperial College London)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Plos Pathogens , VOL 7

State: Published (Approved)
Published: December 2011

Open Access Open Access

Abstract: Vaccinia virus (VACV) protein N1 is an intracellular virulence factor and belongs to a family of VACV B-cell lymphoma (Bcl)-2-like proteins whose members inhibit apoptosis or activation of pro-inflammatory transcription factors, such as interferon (IFN) regulatory factor-3 (IRF-3) and nuclear factor-κB (NF-κB). Unusually, N1 inhibits both apoptosis and NF-κB activation. To understand how N1 exerts these different functions, we have mutated residues in the Bcl-2-like surface groove and at the interface used to form N1 homodimers. Mutagenesis of the surface groove abolished only the N1 anti-apoptotic activity and protein crystallography showed these mutants differed from wild-type N1 only at the site of mutation. Conversely, mutagenesis of the dimer interface converted N1 to a monomer and affected only inhibition of NF-κB activation. Collectively, these data show that N1 inhibits pro-inflammatory and pro-apoptotic signalling using independent surfaces of the protein. To determine the relative contribution of each activity to virus virulence, mutant N1 alleles were introduced into a VACV strain lacking N1 and the virulence of these viruses was analysed after intradermal and intranasal inoculation in mice. In both models, VACV containing a mutant N1 unable to inhibit apoptosis had similar virulence to wild-type virus, whereas VACV containing a mutant N1 impaired for NF-κB inhibition induced an attenuated infection similar to that of the N1-deleted virus. This indicates that anti-apoptotic activity of N1 does not drive virulence in these in vivo models, and highlights the importance of pro-inflammatory signalling in the immune response against viral infections.

Journal Keywords: Apoptosis; Cell; Humans; Mice; Mutation; NF-kappa; Protein; Tertiary; Vaccinia; Viral; Virulence

Diamond Keywords: Vaccinia Virus; Viruses

Subject Areas: Biology and Bio-materials

Instruments: I03-Macromolecular Crystallography

Other Facilities: ESRF

Added On: 04/04/2012 12:08


Discipline Tags:

Pathogens Infectious Diseases Health & Wellbeing Structural biology Life Sciences & Biotech

Technical Tags:

Diffraction Macromolecular Crystallography (MX)