FIG. 8.

RB represses a U6 snRNA gene promoter in vivo, even in the presence of TSA. SAOS2 cells were transfected with pU6/Hae/RA.2 (0.5 μg), pCAT (4 μg), and 8 μg of pSG5L-HA-RB(wt), encoding wild-type RB (lanes 2 and 4), or 8 μg of pSG-RB;567L, encoding an inactive RB null mutant (lanes 1 and 3). In lanes 3 and 4, the cells were maintained in 200 nM TSA for 24 h prior to harvesting. Levels of RNA derived from pU6/Hae/RA.2 and pCAT were assayed by primer extension and then quantitated using a phosphorimager. Values shown represent the signal for U6 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 (lane 1), which is designated 100%, and are means from two experiments.