title: Expression of polyoma virus middle-T antigen in Saccharomyces cerevisiae.
abstract: The polyoma middle-T gene, lacking its intron, was inserted into a yeast expression plasmid containing the phosphoglycerate kinase promoter. Such plasmids transformed yeast at low frequency and these transformants expressed middle-T antigen at a level of approximately 0.1% cell protein. Furthermore, expression of this protein was frequently lost during growth in liquid culture and this loss of middle-T was accompanied by a twofold increase in the rate of growth. The spontaneous production of a truncated middle-T antigen, lacking the C terminus, was also observed; the expression of this protein did not inhibit the growth rate of the cells. Recovery and analysis of the expression plasmids encoding the truncated molecule showed that a single C X G base pair had been deleted from a run of nine consecutive C X G base pairs (Pyr nucleotide 1239--1247) within the middle-T coding region. This frame-shift mutation results in premature termination of the protein and loss of the strongly hydrophobic region of the molecule believed to be responsible for the membrane association of middle-T antigen.
mesh_terms: D000952:Antigens, Polyomavirus Transforming; D000957:Antigens, Viral, Tumor / Q000096:biosynthesis / Q000235:genetics*; D001483:Base Sequence; D004279:DNA, Viral; D005796:Genes; D005822:Genetic Vectors; D006207:Half-Life; D007120:Immunochemistry; D009856:Oncogene Proteins, Viral / Q000096:biosynthesis / Q000235:genetics*; D010957:Plasmids; D011120:Polyomavirus / Q000235:genetics / Q000276:immunology*; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D014170:Transformation, Genetic
chemical_list: D000952:Antigens, Polyomavirus Transforming; D000957:Antigens, Viral, Tumor; D004279:DNA, Viral; D009856:Oncogene Proteins, Viral