Author:

Keywords:

Science & Technology, Life Sciences & Biomedicine, Genetics & Heredity, Antibody Specificity, Antigen-Antibody Reactions, Antigens, Viral, Bacteriophage lambda, Escherichia coli, Molecular Weight, Operon, Plasmids, Protein Biosynthesis, Simian virus 40, 0604 Genetics, 0606 Physiology, 1108 Medical Microbiology, Developmental Biology, 3101 Biochemistry and cell biology, 3102 Bioinformatics and computational biology, 3105 Genetics

Abstract:

Several plasmids were constructed in which the SV40 small-t antigen gene was inserted in close proximity downstream from the thermoinducible leftward promoter (pL) of bacteriophage lambda. Upon temperature induction the best of our constructions expressed a small-t-related 19 000-dalton polypeptide in an amount corresponding to approx. 2.5% of total de novo protein synthesis. This 19 000-dalton protein was identified as small-t by specific immunoprecipitation with anti-T serum and by two-dimensional fingerprint analysis. In addition to the 19 000-dalton product, representative plasmids expressed fairly large amounts (up to 7% of total de novo protein synthesis) of a protein with an apparent Mr of 14 500. This 14 500-dalton polypeptide was shown to be related to authentic small-t. Presumably the secondary structure of the mRNA starting at pL is such that translation initiation at an internal AUG codon of the small-t gene is favored over initiation at the true initiating codon.