FIG. 3.

RB can repress Pol III transcription of a transfected VA1 gene in the presence of TSA. SAOS2 cells were transfected with pVA1 (0.5 μg), pCAT (4 μg), and 8 μg of pSG5L-HA-RB(wt), encoding wild-type RB (bars 2 and 4), or 8 μg of pSG-RB;567L, encoding an inactive RB null mutant (bars 1 and 3). Cells depicted by bars 3 and 4 were maintained in 100 nM TSA for 24 h prior to harvesting. VA1 and CAT RNA levels were assayed by primer extension and then quantitated using a phosphorimager. Values shown represent the signal for VA1 normalized to the levels of CAT expression to correct for transfection efficiency; they are expressed relative to the value obtained in the absence of TSA or functional RB (bar 1), which is designated 100%, and are means from two experiments.