FIGURE 6.

pRb recruitment to the intronic enhancer of Fra-1 is MyoD-dependent. A, pRb is recruited to intron 1 of Fra-1 during differentiation. ChIP analysis of cycling and differentiated C2C12 cells was performed with antibody to pRb or IgG as control. Sequences spanning the E boxes in intron 1 of Fra-1 (Fra-1 int 1), ∼3 kb downstream of the Fra-1 intronic E boxes (Fra-1 3 kb), and the MCK enhancer (MCK) were analyzed by PCR. One-tenth of the lysates used for ChIP were also subjected to PCR (input, In). The results are representative of at least three independent experiments. B, pRb recruitment to intron 1 of Fra-1 is MyoD-dependent. The results shown are as in A, except Rb-positive fibroblasts were infected with MyoD-encoding virus (left panel) or empty vector (right panel). The results are representative of at least three independent experiments. C, as in B, except Rb-deficient fibroblasts were employed. The results are representative of at least three independent experiments.