Table 1.

Implication of NC protein modifications or mutations on the phenotype and/or defects of the viral cycle.

Modifications/Mutations	Phenotype/Defects	Conclusions	References
Cx->Sx or Hy->Ay	Defect in RNA packaging, assembly not correct, defects in NA annealing	More deleterious effects for mutations in ZK1	[12,110,111]
Cx->Hx and Hy->Cy	Normal RNA packaging but virus noninfectious	More deleterious effects for mutations in ZK1	[112,113,114]
ZK2-ZK1 ZK1-ZK1 ZK2-ZK2	Defect in strand-transfer and self-priming reaction during RT	ZK1 must be in the first position, a major role of ZK1 for destabilization activity of NC	[100,115]
ZK2-ZK1 ZK1-ZK1 ZK2-ZK2	Defect in NA annealing	ZK1 must be in the first position, a major role of ZK1 for destabilization activity of NC	[116]
ZK2-ZK1 ZK1-ZK1 ZK2-ZK2	Defects in DNA stretching ability as a test of chaperone activity	ZK1 must be in the first position, a major role of ZK1 for destabilization activity of NC	[117]
NC(1–35)	Sufficient for in vitro chaperone activity	Critical need of ZK1 for chaperone activity	[118]
NC(29–55)	Not able to recognize packaging signal, low affinity for NA	Critical need of ZK1 for interaction with NA	[118,119]
Mutation of Trp37 in ZK2 or Phe16 in ZK1	Defect in NC chaperone activity, NA-binding strongly affected	Critical role of Trp37 in ZK2, less critical for Phe16 in ZK1	[120]
Basic residues	Inhibition of gRNA dimerization, reduction of gRNA packaging, strong effect on virus assembly, reduction of infectivity	Critical for RNA packaging, optimal chaperone activity and infectivity	[101,121,122,123]
Deletion of the linker	Decrease of NA-binding affinity	Linker contributes to NA-binding and chaperone activity of NC	[118]
Deletion of ZK1 and/or ZK2 within Gag	Production of viral particles containing DNA	ZK2 more important than ZK1 to block premature RT	[42,124]
Deletion of ZK1 and/or ZK2 within Gag	Loss of affinity in Gag-gRNA complexes	ZK2 more important to ensure Gag-gRNA complexes of high affinities	[102]
Deletion of ZK1 and/or ZK2 within Gag	Recruitment of Gag-gRNA complexes at the plasma membrane (PM)	ZK2 more important for the accumulation of ribonucleoprotein complexes at the PM	[125]