Chromosomal instability at a mutational hotspot in polyoma middle T-antigen affects its ability to activate the ARF-p53 tumor suppressor pathway

• Published in: Oncogene Vol. 25; no. 10; pp. 1454 - 1462
• Main Authors: RODRIGUEZ-VICIANA, P, COLLINS, C. H, MOULE, M. G, FRIED, M
• Format: Journal Article
• Language: English
• Published: Basingstoke Nature Publishing 09.03.2006; Nature Publishing Group
• Subjects: Amino Acid Sequence; Amino acids; Animals; Antigens; Antigens, Polyomavirus Transforming - genetics; Antigens, Polyomavirus Transforming - physiology; Apoptosis; ARF protein; Base Sequence; Biological and medical sciences; Cancer research; Cell cycle; Cell division; Cell Line; Cell physiology; Cell transformation and carcinogenesis. Action of oncogenes and antioncogenes; Chromosomal Instability - genetics; Cytosine; Early region; Frameshift Mutation; Fundamental and applied biological sciences. Psychology; Gene Expression Regulation - genetics; Genomic instability; Hydrophobicity; Kinases; Medical research; Molecular and cellular biology; Molecular Sequence Data; Mutants; Mutation; Nucleotide sequence; p53 Protein; Phenotypes; Polyomavirus; Polyomavirus - genetics; Proteins; Rats; Reading; Retrovirus; Revertants; Sequence Deletion; Signal Transduction - genetics; Tumor suppressor genes; Tumor Suppressor Protein p14ARF - physiology; Tumor Suppressor Protein p53 - physiology; Tumors; United States > US; San Francisco California; California; Hot spot; hot spot mutations; Carcinogenesis; p53; Infection; TP53 Gene; ARF; Viral disease; chromosomal instability; REF52 cells; Instability; polyoma virus middle T-antigen; Mutation; Middle T antigen; Tumor suppressor gene
• ISSN: 0950-9232; 1476-5594
• DOI: 10.1038/sj.onc.1209197

We have isolated spontaneous mutants of polyoma virus middle T-antigen (PyMT) that do not activate the ARF-p53 pathway based on their inability to block REF52 cell division. The REF52 cells containing these mutants have a flat untransformed morphological phenotype and do not express the ARF protein. The PyMT mutations in the different cell isolates so far analysed occur at a mutational hotspot in the PyMT sequence between nucleotides 1241 and 1249, which contains nine consecutive cytosines. In one set of mutants a single cytosine was deleted, while in another mutant set an additional cytosine was inserted. Both these mutations result in frameshifts, generating altered PyMT proteins containing amino-acid sequences derived from each of the two other alternative reading frames of the polyoma virus early region. Both types of mutations result in the loss of the C-terminal PyMT region containing the membrane-binding hydrophobic region and result is mislocalization of the PyMT mutant proteins. Revertant wild-type PyMT (containing nine cytosines) was easily detected in transformants generated after infection of REF52 cells expressing high amounts of dominant negative p53 with retroviruses containing either mutation. We demonstrate that wild-type PyMT revertants are derived from mutations in the hotspot sequence of the integrated mutant PyMT sequences.