Fig. 3.

Packaging defect of a subset of MHV domain N3 mutants. The sources and descriptions of the various N protein domain N3 or spacer B mutants are given in the text. MMA(1) and MMA(2) are two independent isolates of the MMA mutant (Alb336 and Alb337; Kuo and Masters, 2002). (A and C) Western blots of purified virions probed with anti-N polyclonal and anti-M monoclonal antibodies. (B and E) Northern blots of RNA isolated from immunopurified virions. (D) Northern blot of total RNA isolated from mock-infected or infected 17Cl1 cells harvested at 15 h postinfection. MHV RNA was detected with a probe specific for the 5′ half of the N gene. (F) Alignment of the carboxy termini of wild-type and mutant MHV N proteins; the GenBank accession number for wild-type MHV-A59 is AY700211. Charged amino acids are noted above the alignment. Mutated residues are indicated in color: blue for viruses with wild-type packaging; red for viruses with defective packaging. The segment of N3 essential for packaging competence is indicated by the box. Arrows denote two aspartate residues critical for interaction between the N and M proteins (Hurst et al., 2005).