The molecular analysis of the regulation of nuclear proteins induced by interleukin-6 has provided new insights into this largely unknown signal transduction pathway. Transcription factors of the CCAAT/enhancer-binding protein and AP-1 families, as well as the octamer-binding proteins and the tumor suppressor gene product pRB, are regulated by interleukin-6 in a cell type specific manner, suggesting that they may play a role in the nuclear signaling by interleukin-6.