Failure of HPV E6 to rapidly degrade p53 in human HeLa x PNET cell hybrids.
The ability of the E6 protein from high risk human papillomaviruses (HPVs) to degrade p53 via the ubiquitin pathway plays a major role in the development of cervical carcinomas. We have previously generated cell hybrids between a p53 null peripheral neuroepithelioma (PNET) cell line and a cervical carcinoma HeLa cell line which exhibits efficient E6-mediated degradation of p53. All of the resulting hybrids expressed HPV 18 E6 from the HeLa parent and some of the hybrids additionally expressed HPV 16 E6. Surprisingly, in spite of abundant E6 expression, the hybrids expressed relatively high steady-state levels of the wild-type p53 protein. We then examined the hybrids to determine whether other components of the E6-mediated degradation pathway were missing or nonfunctional. Specifically, we determined that the E6-associated protein (E6-AP), essential for E6-mediated degradation, was expressed. We further verified that these hybrids had a functional ubiquitination pathway, which suggests that this phenomenon is not due to a general defect in this pathway. We therefore conclude that other unidentified, possibly cell-specific factors can play a role in the E6-mediated degradative process and may act to inhibit this process.
Isaacs
J S
JS
Department of Biochemistry and Biophysics and the UNC-Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill 27599, USA.
Chen
P
P
Garza
A
A
Hansen
M F
MF
Barrett
J C
JC
Weissman
B E
BE
D004249:DNA Damage; D004268:DNA-Binding Proteins; D019084:Fluorescent Antibody Technique, Indirect; D015972:Gene Expression Regulation, Neoplastic; D016158:Genes, p53; D006367:HeLa Cells; D006801:Humans; D006822:Hybrid Cells; D018241:Neuroectodermal Tumors, Primitive, Peripheral / Q000473:pathology; D009856:Oncogene Proteins, Viral / Q000378:metabolism*; D018807:Polymorphism, Single-Stranded Conformational; D016755:Proto-Oncogene Proteins c-jun / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics; D011839:Radiation, Ionizing; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*; D014452:Ubiquitins / Q000378:metabolism
D004268:DNA-Binding Proteins; C052603:E6 protein, Human papillomavirus type 18; D009856:Oncogene Proteins, Viral; D016755:Proto-Oncogene Proteins c-jun; D012333:RNA, Messenger; D016159:Tumor Suppressor Protein p53; D014452:Ubiquitins