Investigating the role of MafK subnuclear relocalization during erythroid differentiation

MafK, a transcription factor that regulates beta-globin gene expression, undergoes subnuclear relocalization from heterochromatic to euchromatic regions during erythroid differentiation. As a first step to deciphering the role of MafK subnuclear relocalization, we investigated the characteristics of MafK heterochromatic localization before differentiation. Immunoprecipitation and mass spectrometry experiments indicate that MafK exists as a homodimer in the heterochromatic fraction, distinguishing it from MafK at the beta-globin locus. Immunofluorescence microscopy results demonstrate that a functional DNA-binding domain is necessary for MafK heterochromatic targeting. Native chromatin immunoprecipitation and quantitative PCR results suggest that MafK localizes to heterochromatin by binding pericentromeric major satellite DNA. A bioinformatics search for known Maf recognition elements indicates that pericentromeric heterochromatin contains novel MafK binding site(s). Our results support a role for subnuclear relocalization in regulating the spatial distribution and local concentration of MafK, presumably as an additional level of control over beta-globin gene expression, during erythroid differentiation. ii...