The proposed role of the PYR complex in human hemoglobin switching. The circles indicate unspecified chromatin remodeling complexes and transcription factors. The details of these interactions in chromatin between the βLCR elements, globin structural genes, erythroid transcription factors, and these chromatin remodeling complexes are unknown. In fetal-embryonic cells, the human βLCR is associated with the γ-globin gene loci downstream. The blue circles include the potential activities of FKLF and SSP in this process at the γ-globin promoter. In adult-type cells, the βLCR associates with and activates β-globin gene expression. New interactions leading to repression of γ-globin gene expression occur, and PYR complex binding and its HDACs may contribute to this process. The SWI/SNF complex subunits, the NURD subunits, and the DNA-binding subunit Ikaros of the PYR complex are shown.