The HPV-16 E6 and E6-AP complex functions as a ubiquitin-protein ligase in the ubiquitination of p53.
The ubiquitin-dependent proteolytic pathway plays a major role in selective protein degradation. Ubiquitination of proteins requires the sequential action of the ubiquitin-activating enzyme (E1), ubiquitin-conjugating enzymes (E2), and in some cases ubiquitin-protein ligases (E3s). The oncogenic human papillomavirus (HPV) types 16 and 18 utilize this cellular proteolytic system to target the tumor suppressor protein p53. The HPV E6 oncoprotein binds to a cellular protein of 100 kd, termed E6-associated protein (E6-AP). The E6-E6-AP complex specifically interacts with p53, resulting in the rapid ubiquitin-dependent degradation of p53. Here we report the purification and identification of the factors necessary for the E6-E6-AP-mediated ubiquitination of p53. The ubiquitination of p53 requires the E1 enzyme and a novel E2 in mammalian cells, while E3 activity is conferred by the E6-E6-AP complex. Furthermore, E6-AP appears to have ubiquitin-protein ligase activity in the absence of E6.
Scheffner
M
M
Laboratory of Tumor Virus Biology, National Cancer Institute, Bethesda, Maryland 20892.
Huibregtse
J M
JM
Vierstra
R D
RD
Howley
P M
PM
D002460:Cell Line; D006801:Humans; D008025:Ligases / Q000302:isolation & purification / Q000378:metabolism*; D046911:Macromolecular Substances; D008954:Models, Biological; D009856:Oncogene Proteins, Viral / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012097:Repressor Proteins; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*; D014451:Ubiquinone / Q000378:metabolism*; D044764:Ubiquitin-Activating Enzymes; D044763:Ubiquitin-Conjugating Enzymes; D044767:Ubiquitin-Protein Ligases; D014764:Viral Proteins / Q000378:metabolism*
C068651:E6 protein, Human papillomavirus type 16; D046911:Macromolecular Substances; D009856:Oncogene Proteins, Viral; D011993:Recombinant Fusion Proteins; D012097:Repressor Proteins; D016159:Tumor Suppressor Protein p53; D014764:Viral Proteins; D014451:Ubiquinone; D044763:Ubiquitin-Conjugating Enzymes; C471639:UBE3A protein, human; D044767:Ubiquitin-Protein Ligases; D008025:Ligases; D044764:Ubiquitin-Activating Enzymes