Patent ID: 8357535

Claim:
A method of screening cells for expression of a protein of interest, said method comprising the steps of: a) transfecting cells by an expression vector encoding: (i) a Puro-DHFR chimeric protein comprising: SEQ ID NO: 2; or a functional polypeptide fragment of dihydrofolate reductase (DHFR) fused to a functional polypeptide fragment conferring resistance to puromycin (Puro), wherein said functional polypeptide fragment of dihydrofolate reductase comprises SEQ ID NO: 6, and said functional polypeptide fragment of puromycin N-acetyl transferase comprises SEQ ID NO:4; and (ii) a protein of interest; b) selecting cells being resistant to puromycin; and c) assaying the fluorescence of the cells selected in step (b) with a fluorescent compound binding to DHFR.