tokens: We have demonstrated that the monocyte-specific expression of the CSF-1 receptor is regulated at the level of transcription by a tissue-specific promoter whose activity is stimulated by the monocyte/B-cell-specific transcription factor PU.1 ( D.-E.Zhang , C.J.Hetherington , H.-M.Chen , and D.G.Tenen , Mol.Cell. Biol.14 : 373-381 , 1994 ) .