A mutated form of the human cyclin D1 cDNA, preceded by sequence for an N-terminal 3xFLAG tag and followed by SV40 poly(A) signal sequences, was placed downstream of the tetracycline responsive element. The mutation is a G-to-A mutation that changes lysine codon 112 to a glutamic acid codon (p.K112E), eliminating or severely reducing the protein's phosphorylation (kinase) activity. (J:309458)