Nucleic Acids Research, 1985, Vol. 13, No. 2 501-519
© 1985
Articles |
Expression of polyoma early gene products in E. coli
1Department of Biochemistry and Pharmacology, Tufts University School of Medicine Boston, MA 02111, USA 2Department of Pathology, Harvard Medical School Boston, MA 02115, USA 3Dana-Farber Cancer Institute Boston, MA 02115, USA
*To whom correspondence should be addressed
Received September 4, 1984. Revised December 11, 1984. Accepted December 11, 1984.
The three products of the early region of polyoma virus have been cloned for expression in E. coli using the Tac promoter. Although the identical promoter and ribosome binding site are used in each final construction, the observed level of protein expression is different for each protein. While plasmids expressing wild type T antigens as well as a plasmid expressing the truncated Py-1387T middle T antigen lacking the membrane-anchoring sequence give rise to synthesis of proteins readily detectible by 95S-methionine labeling and immunoprecipitation, only small P and the middle T of Py-1387T are made in amounts sufficient for ready detection in total cell protein. Unlike middle T expressed in animal cells, middle T produced in E. coli is not detectibly phosphorylated. Further, the E. coli protein lacks tyrosine kinase activity.