[Expression in Chinese hamster transformant TK+-cells of the bacterial gene for beta-lactamase]

Using monospecific immune antiserum the expression of beta-lactamase bacterial gene (from the plasmid pBR322) in transformed TK+ Chinese hamster cells was studied. It is shown that in some TK+-clones the beta-lactamase gene is expressed and this expression is stimulated by an inhibitor of DNA methylation-5-azacytidine. Two physically linked genes (the Herpes simplex thymidine kinase gene, and the beta-lactamase gene) introduced into the Chinese hamster cells on the same plasmid are found to be expressed independently.