Figure 2.

Mef2D and p38 are rate limiting for the activation of late-stage genes. (A) MDER cells were infected with MKK6E and/or Mef2D-expressing retrovirus as indicated, induced to differentiate for varying lengths of time, and analyzed by Northern blot with the indicated probes. GFP is used as a control retrovirus. (B) MDER fibroblasts were transfected with the MKK6E and/or Mef2D retrovirus as indicated, induced to differentiate, and examined by immunofluorescence for the indicated late-stage (Myh3 and Des) and early-stage (Mgn) gene products. The bars indicate the average number of positive cells per field.