The BPV-1 E2 DNA-contact helix cysteine is required for transcriptional activation but not replication in mammalian cells.
The papillomavirus E2 protein contains an amino-terminal region thought necessary and sufficient to support transcriptional activation and a carboxy-terminal region shown to direct sequence-specific DNA binding and dimerization. A cysteine residue in the center of the E2 DNA recognition helix is highly conserved among papillomavirus E2 proteins. Mutations of this cysteine in bovine papillomavirus type 1 E2 to serine and glycine resulted in proteins which failed to activate E2-dependent promoters in mammalian cells. These E2 mutants were DNA-binding competent, dimeric, and nuclear. When fused to the VP16 transactivation domain, C-terminal regions of E2 containing the mutations at 340 supported transcriptional activation, indicating that the heterologous trans-activation domain did not require cysteine in the DNA-binding helix as did the full-length E2 transactivating protein. Although cysteine-340 was required for transcriptional activation it was not required for DNA replication in vivo. Together, these results suggest that the E2 DNA-binding domain may directly contribute to functions of transcriptional activation previously thought limited to the N-terminal domain.
Grossel
M J
MJ
Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts 02111, USA.
Barsoum
J
J
Prakash
S S
SS
Androphy
E J
EJ
D016475:3T3 Cells; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D052688:Bovine papillomavirus 1 / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D016466:CHO Cells; D002460:Cell Line; D006224:Cricetinae; D003545:Cysteine / Q000378:metabolism*; D004261:DNA Replication; D004279:DNA, Viral / Q000096:biosynthesis / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008322:Mammals; D051379:Mice; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D012441:Saccharomyces cerevisiae / Q000235:genetics; D015533:Transcriptional Activation; D014764:Viral Proteins / Q000235:genetics / Q000378:metabolism*; D014779:Virus Replication
D004279:DNA, Viral; D004268:DNA-Binding Proteins; C051550:E2 protein, Bovine papillomavirus; D014764:Viral Proteins; D003545:Cysteine