Abstract
Human papillomavirus type 18 (HPV-18) E7 proteins bind zinc through Cys-X-X-Cys repeats located at the C terminus of the protein. In order to examine the role of these cysteine motifs in E7 function, we expressed the HPV-18 E7 protein in bacteria and found that purified E7 forms a dimer through interactions with zinc. Mutants with single mutations within the Cys-X-X-Cys motifs bound a reduced level of zinc in a zinc blot assay, while a double mutant lost all zinc-binding activity. When expressed in vivo, none of the mutants cooperated with an activated ras oncogene to transform primary rat embryo fibroblasts, but all mutants retained nearly wild-type Rb-binding activity. The results indicate that the cysteine motifs play an important role in transformation by HPV-18 E7 but do not contribute to Rb binding.
Publication types
-
Comparative Study
-
Research Support, Non-U.S. Gov't
-
Research Support, U.S. Gov't, P.H.S.
MeSH terms
-
Adenovirus E1A Proteins / genetics
-
Amino Acid Sequence
-
Animals
-
Cell Transformation, Viral*
-
Cells, Cultured
-
Conserved Sequence
-
Cysteine / metabolism*
-
DNA Mutational Analysis
-
DNA-Binding Proteins*
-
Edetic Acid / pharmacology
-
Escherichia coli / genetics
-
Half-Life
-
Models, Chemical
-
Molecular Sequence Data
-
Oncogene Proteins, Viral / genetics
-
Oncogene Proteins, Viral / isolation & purification
-
Oncogene Proteins, Viral / metabolism*
-
Oncogene Proteins, Viral / pharmacokinetics
-
Protein Conformation / drug effects
-
Rats
-
Recombinant Proteins / metabolism
-
Repetitive Sequences, Nucleic Acid*
-
Retinoblastoma Protein / metabolism
-
Rubidium / metabolism*
-
Zinc / metabolism*
Substances
-
Adenovirus E1A Proteins
-
DNA-Binding Proteins
-
E7 protein, Human papillomavirus type 18
-
Oncogene Proteins, Viral
-
Recombinant Proteins
-
Retinoblastoma Protein
-
Edetic Acid
-
Zinc
-
Cysteine
-
Rubidium