ABSTRACT
PURPOSE: To gain insight on the role of AP-1 in transcriptional regulation of vimentin gene during differentiation of HL-60 cells by 12-0-tetradecanoylphorbol-13-acetate (TPA), the levels of vimentin mRNA and AP-1 have been investigated with Northern blot hybridization and DNA mobility shift assay. MATERIALS AND METHODS: HL-60 cells were grown in RPMI 1640 medium supplemented with 10% heat-inactivated fetal calf serum and antibiotics in a humidified 5% CO2 at 37 degree C. Total RNA was prepared by a modification of the method of Karlinsey et al. Northern blot hybridization was performed by the method of Virca et al. EcoRI fragment of pVIM-GEM was used as probe for vimentin mRNA. DNA mobility shift assay was performed by the method of Lim et al. End labeled DNA probe(Upper strand, 5'-CGCTTGATGAGTCAGCCG- 3') for AP-1 binding activity was mixed with nuclear extracts in a 20 microliter reaction volume containing 300 mM KC1, 60 mM HEPES, pH 7.9, 25 mM MgCl2, 1 mM EDTA, 1 mM DTT, 60% glycerol, and 2 microgram of poly[dI-dC]. RESULTS: TPA increased vimentin mRNA levels, with maxima1 stimulation reached at 24 hr. The level of vimentin mRNA was induced in proportion to the concentration of TPA. TPA-induced vimentin mRNA was almost reduced by actinomycin-D pretreatment. TPA- induced stimulation of vimentin gene was completely reduced by staurosporin pretreatment. In DNA mobility shift assay, AP-I newly appeared at 24 hr during TPA- induced differentiation and was almost not detected after the pretreatment of staurosporin. CONCLUSIONS: These results suggest that the induction of vimentin mRNA during TPA- dependent differentiation in HL-60 cells may be mediated by protein kinases C signal transduction and AP-1 is important to transcriptional regulation.