FIGURE 1.

MCM5 and MCM2 are essential for general transcription. A, 293T cells were left untreated or transfected with either a negative control siRNA or MCM5 siRNA. Whole cell extracts were prepared after 4 days, and Western blot analysis was performed with anti-MCM5, anti-MCM3, anti-Stat1, and anti-Stat3 antibodies. B, 293T cells transfected as described in A were treated with 50 μm [5,6-H-3]uridine 40–50 Ci/mmol for 5, 20, and 120 min. Cells were washed once with 1× phosphate-buffered saline and resuspended in 500 μl of 10% trichloroacetic acid. The precipitated nucleotides were collected with glass microfiber filters, and cpm were determined with a scintillation counter. Data represent the averages and standard deviations (error bars) of three experiments. C, 293T cells were transfected with either a negative control siRNA or MCM2 siRNA and cultured for 3 days, and Western blot was performed with anti-MCM2, anti-MCM5, and anti-Stat3 antibodies. D, cells transfected as described in C were analyzed by tritium incorporation assays as described in B.