The HIV 'A' (sor) gene product is essential for virus infectivity

Nature. 1987 Aug 20-26;328(6132):728-30. doi: 10.1038/328728a0.


The genome of the human immunodeficiency virus (HIV) contains several open reading frames (ORFs) not present in other viruses. The 'A' gene, also known as Q2 P'3, ORF-1(4) or sor5, partially overlaps the pol gene; its protein product has a relative molecular mass of 23,000 (Mr 23K) and is present in productively infected cells. The function of this protein is unclear; mutant viruses deleted in 'A' replicate in and kill CD4+ lymphocyte lines, but the high degree of conservation of the deduced amino-acid sequence in nine different HIV isolates (80%) and the presence of analogous genes in HIV-2 and other lentiviruses suggest that the gene function is an important one. Here we describe a mutant virus deficient in the 'A' gene which produces virion particles normally; however, the particles are approximately 1,000 times less infective than wild type. Transcomplementation experiments partially restore infectivity. The mutant virus spreads efficiently when virus-producing cells are co-cultivated with CD4+ lymphocytes, however, indicating that HIV can spread from cell to cell in a mechanism that does not require the 'A' gene product and probably does not require the production of infective virus particles.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Cell Communication
  • Chromosome Deletion
  • Cloning, Molecular
  • Colonic Neoplasms / genetics
  • Genetic Complementation Test
  • HIV / genetics*
  • Humans
  • Mutation
  • Phenotype
  • RNA-Directed DNA Polymerase / metabolism
  • Recombination, Genetic
  • Transfection
  • Virion / analysis


  • RNA-Directed DNA Polymerase