to DNA containing the long terminal repeat (LTR) of mouse mammary tumor virus (MMTV)
have been constructed. Transformants of NIH 3T3 cells induced by transfection with MMTV
LTRp21 hybrid DNA have been identified that express the normal p21 gene product. The
levels of p21 RNA and protein in these transformants are regulated by physiological
concentrations of dexamethasone, a synthetic glucocorticoid hormone. Hybrid transcripts …