Structure of the human myeloid CSF receptor promoters. As with many myeloid promoters, relatively small regions direct activity and specificity in transient transfection studies; in addition, there is no well-defined TATA box. The major transcription start site is designated by the horizontal arrow. Shown are the locations of binding sites for PU.1, C/EBP, and AML1. The PU.1 site in the G-CSF receptor promoter is located in the 5′ untranslated region, at bp +3653; a functional PU.1 site is also found in the 5′ UT region of the PU.1 promoter.55 In unstimulated myeloid cell lines, the major C/EBP gene product is C/EBPα.53,54,215 In newborn livers from C/EBPα −/− animals, only expression of the G-CSF receptor is significantly reduced.28 In PU.1 −/− animals and ES cells, expression of the M-CSF receptor is significantly reduced or undetectable.162 163
