Cytopathic effect in human papillomavirus type 1-induced inclusion warts: in vitro analysis of the contribution of two forms of the viral E4 protein.
Myrmecia warts induced by human papillomavirus type 1 (HPV1) are characterized by abundant eosinophilic inclusions associated with HPV1 E4 gene products. The major HPV1 E4 proteins are a 17-kilodalton (kDa) E1-E4 fusion protein and a 16-kDa species lacking the five E1 amino acids and a few E4 residues. To study the contribution of E4 proteins to the formation of myrmecia inclusions, we used a previously designed transient expression system in the rabbit VX2-R keratinocyte line. We find that the E1-E4 and an E4 protein without the E1 residues (E4-3200) form eosinophilic inclusions. Ultrastructural and immunoelectron microscopic studies show that the electron-dense, keratohyalin-like myrmecia inclusions are recognized by anti-E4 antibodies. They are associated with tonofilament bundles at their periphery in the cytoplasm or free of filaments in the nucleus. The E1-E4 inclusions formed in vitro are also homogeneously electron dense, and are usually associated with tonofilaments at their periphery in the cytoplasm and free of filaments in the nucleus. The E4-3200 inclusions are exclusively cytoplasmic and heterogeneously electron dense, with a fibrillar structure made of entangled 10-nm filaments. The expression of either protein in VX2-R cells does not result in the collapse of the cytokeratin network, as shown by immunofluorescence double-labeling experiments. This is in contrast to data reported for the HPV16 E1-E4 protein. Our findings indicate that the E1-E4 protein by itself accounts for the formation of myrmecia inclusions, and suggest that the five N-terminal E1 amino acids play a major role in the interaction of E4 proteins with intermediate filaments.
Rogel-Gaillard
C
C
Unité INSERM 190, Institut Pasteur, Paris, France.
Pehau-Arnaudet
G
G
Breitburd
F
F
Orth
G
G
D017504:Adenovirus E4 Proteins / Q000032:analysis / Q000502:physiology; D000595:Amino Acid Sequence; D000818:Animals; D002460:Cell Line; D003588:Cytopathogenic Effect, Viral; D003594:Cytoplasmic Granules / Q000187:drug effects / Q000648:ultrastructure; D005455:Fluorescent Antibody Technique; D006801:Humans; D002479:Inclusion Bodies / Q000737:chemistry; D015603:Keratinocytes / Q000166:cytology; D007633:Keratins / Q000502:physiology; D016253:Microscopy, Immunoelectron / Q000379:methods; D008969:Molecular Sequence Data; D027383:Papillomaviridae / Q000502:physiology* / Q000648:ultrastructure; D011817:Rabbits; D014407:Tumor Cells, Cultured
D017504:Adenovirus E4 Proteins; D007633:Keratins