Fig. 8. A model of how Abl mediates mitogenesis in response to growth factors. Growth factor (GF)-induced SFK activation allows phosphorylation of Abl in the cytoplasm for increased catalytic activity. Abl then operates on a Rac/JNK and Rac/Nox pathway for Myc expression, a transcription factor required for induction of DNA synthesis. JNK and Nox may participate in Myc induction through mRNA stabilization and/or gene transcription. Note that Abl substrates for Rac activation are currently unknown. SFK-induced Myc implicates additional substrates, including Stat3 and Shc. The Ras signaling cascade may participate in mitogenesis through Myc protein stabilization and expression of other genes.