Identification and characterization of the Bel 3 protein of human foamy virus.
The human foamy virus (HFV) is a complex retrovirus that contains several regulatory and auxiliary bel genes besides the gag, pol, and env genes. In contrast to the gene products of bel 1 and bel 2/bet that were identified previously, the Bel 3 protein has not been described to date. Here we report the identification of Bel 3 in HFV-infected cells by immunoprecipitation, indirect immunofluorescence, and expression cloning under the control of a strong heterologous promoter. Bel 3 was immunoprecipitated with an antiserum directed against a bacterially expressed and purified form of recombinant Bel 3 antigen. Bel 3 was found to be expressed in low amounts in the cytoplasm of HFV-infected cells and to migrate with an apparent molecular mass of 19.4 kDa on electrophoresis in SDS-polyacrylamide gels, consistent with the calculated value of 18.2 kDa. Radioimmunoprecipitation of HFV-infected cell lysates with the hyperimmune serum against Bel 3 revealed at least two additional immunoreactive bands of 15.5 and 10.6 kDa. The results indicate that Bel 3 was labile, because it was partially degraded even at early time points after infection. On transfection and expression in transfected COS cells, recombinant Bel 3 was immunoprecipitated and migrated in three polypeptide bands of 18.7, 14.8, and 9.3 kDa under denaturing conditions. In the absence of reducing agents, the bacterially expressed and purified recombinant Bel 3 protein of 16.1 kDa can form homodimers of 30 kDa.
Weissenberger
J
J
Abteilung Retrovirale Genexpression, Forschungsschwerpunkt Angewandte Tumorvirologie, Deutsches Krebsforschungszentrum, Heidelberg, Germany.
Flügel
R M
RM
D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D003001:Cloning, Molecular; D017931:DNA Primers / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics; D015870:Gene Expression; D005814:Genes, Viral; D006801:Humans; D007150:Immunohistochemistry; D008969:Molecular Sequence Data; D008970:Molecular Weight; D012191:Retroviridae Proteins / Q000235:genetics* / Q000276:immunology / Q000302:isolation & purification; D016092:Spumavirus / Q000235:genetics* / Q000276:immunology; D014162:Transfection
D017931:DNA Primers; D012191:Retroviridae Proteins