title: Context-dependent regulation of GATA-1 by friend of GATA-1.
abstract: The transcription factor GATA-1 and its cofactor, friend of GATA-1 (FOG-1), are essential for normal erythroid development. FOG-1 physically interacts with GATA-1 to augment or inhibit its activity. The mechanisms by which FOG-1 regulates GATA-1 function are unknown. By using an assay that is based on the phenotypic rescue of a GATA-1-null erythroid cell line, we found that a conditional form of GATA-1 (GATA-1-ER) strongly induced histone acetylation at the beta-major globin promoter in vivo, consistent with previous results. In contrast, GATA-1 bearing a point mutation that impairs FOG-1 binding [GATA-1(V205M)-ER] failed to induce high levels of histone acetylation at this site. However, at DNase I-hypersensitive site (HS)3 of the beta-globin locus control region, GATA-1-induced histone acetylation was FOG-1-independent. Because the V205M mutation does not disrupt GATA-1 binding to DNA templates in vitro, we were surprised to find that in vivo GATA-1(V205M)-ER fails to bind the beta-globin promoter. However, at HS3, DNA binding by GATA-1 was FOG-1-independent, thus correlating histone acetylation with GATA-1 occupancy. Examination of additional GATA-1-dependent regulatory elements showed that the interaction with FOG-1 is required for GATA-1 occupancy at select sites, such as HS2, but is dispensable at others, including the FOG-1-independent GATA-1 target gene EKLF. Remarkably, at the GATA-2 gene, which is repressed by GATA-1, interaction with FOG-1 was dispensable for GATA-1 occupancy and was required for transcriptional inhibition and histone deacetylation. These results indicate that FOG-1 employs distinct mechanisms when cooperating with GATA-1 during transcriptional activation and repression.
authors.affiliation: University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA.
authors.forename: Danielle L
authors.initials: DL
authors.lastname: Letting
authors.forename: Ying-Yu
authors.initials: YY
authors.lastname: Chen
authors.forename: Carrie
authors.initials: C
authors.lastname: Rakowski
authors.forename: Sarah
authors.initials: S
authors.lastname: Reedy
authors.forename: Gerd A
authors.initials: GA
authors.lastname: Blobel
mesh_terms: D000107:Acetylation; D001483:Base Sequence; D002352:Carrier Proteins / Q000502:physiology*; D002460:Cell Line; D017931:DNA Primers; D004268:DNA-Binding Proteins / Q000235:genetics / Q000502:physiology*; D050981:Erythroid-Specific DNA-Binding Factors; D005914:Globins / Q000235:genetics; D006657:Histones / Q000378:metabolism; D009687:Nuclear Proteins / Q000502:physiology*; D017354:Point Mutation; D014157:Transcription Factors / Q000235:genetics / Q000502:physiology*
chemical_list: D002352:Carrier Proteins; D017931:DNA Primers; D004268:DNA-Binding Proteins; D050981:Erythroid-Specific DNA-Binding Factors; D006657:Histones; D009687:Nuclear Proteins; D014157:Transcription Factors; C498432:ZFPM1 protein, human; D005914:Globins