A second-site suppressor significantly improves the defective phenotype imposed by mutation of an aromatic residue in the N-terminal domain of the HIV-1 capsid protein.
The HIV-1 capsid (CA) protein plays an important role in virus assembly and infectivity. Previously, we showed that Ala substitutions in the N-terminal residues Trp23 and Phe40 cause a severely defective phenotype. In searching for mutations at these positions that result in a non-lethal phenotype, we identified one candidate, W23F. Mutant virions contained aberrant cores, but unlike W23A, also displayed some infectivity in a single-round replication assay and delayed replication kinetics in MT-4 cells. Following long-term passage in MT-4 cells, two second-site mutations were isolated. In particular, the W23F/V26I mutation partially restored the wild-type phenotype, including production of particles with conical cores and wild-type replication kinetics in MT-4 cells. A structural model is proposed to explain the suppressor phenotype. These findings describe a novel occurrence, namely suppression of a mutation in a hydrophobic residue that is critical for maintaining the structural integrity of CA and proper core assembly.
Tang
Shixing
S
Viral Gene Regulation Section, Laboratory of Molecular Genetics, National Institute of Child Health and Human Development, National Institutes of Health, Building 6B, Room 216, Bethesda, MD 20892-2780, USA.
Ablan
Sherimay
S
Dueck
Megan
M
Ayala-López
Wilfredo
W
Soto
Brenda
B
Caplan
Margaret
M
Nagashima
Kunio
K
Hewlett
Indira K
IK
Freed
Eric O
EO
Levin
Judith G
JG
D036022:Capsid Proteins / Q000737:chemistry* / Q000235:genetics*; D002460:Cell Line; D015497:HIV-1 / Q000235:genetics* / Q000502:physiology* / Q000648:ultrastructure; D006801:Humans; D050296:Microbial Viability / Q000235:genetics; D046529:Microscopy, Electron, Transmission; D008958:Models, Molecular; D009154:Mutation; D010641:Phenotype; D017434:Protein Structure, Tertiary; D012194:RNA-Directed DNA Polymerase / Q000032:analysis; D013489:Suppression, Genetic; D014771:Virion / Q000648:ultrastructure; D014779:Virus Replication
D036022:Capsid Proteins; D012194:RNA-Directed DNA Polymerase