Cell division is dependent on cell growth. Although elements regulating cell division have received intense scrutiny, factors regulating growth in the form of new protein synthesis are less well characterized. The mRNA cap-binding protein (eIF4E) is rate limiting for translation initiation and transforms fibroblasts. To identify factors regulating eIF4E, we characterized the promoter of the eIF4E gene using linker scanning mutants. Promoter activity was dependent on sites at -5, -25, -45 and -75. Sites at -5, -25, and-45 were located in areas classi-cally involved in transcription initiation; a myc box at -75 was previously described. Since the eIF4E promoter lacked both TATAA and initiator elements, we characterized potential preinitiation complexes at -5, -25 and -45 sites. EMSA experiments revealed novel factors binding the -25 site whose minimum motif was TTACCCCCCCTT. The abundance of 68 and 98 kd proteins which bound this site in UV crosslinking and Southwestern analysis correlated with protein synthesis rates and c-myc levels in differentiating U937 and HL60 cells. Correlations between the 68 and 98 kd proteins, eIF4E expression and protein synthesis rates suggested a role for the -25-binding factors in down-regulation of protein synthesis during differentiation. These novel transcription factors are also positioned to mediate the induction of eIF4E by the c-myc oncogene.