A Positive Role for NLI/Ldb1 in Long-Range β-Globin Locus Control Region Function

• Published in: Molecular cell 2007-12, Vol.28 (5), p.810-822
• Main Authors: Song, Sang-Hyun, Hou, Chunhui, Dean, Ann
• Format: Article
• Language: English
• Subjects: Adaptor Proteins, Signal Transducing; Basic Helix-Loop-Helix Transcription Factors - genetics; Basic Helix-Loop-Helix Transcription Factors - metabolism; Cell Differentiation; Chromatin - metabolism; Chromatin Immunoprecipitation; DNA; DNA-Binding Proteins - antagonists & inhibitors; DNA-Binding Proteins - genetics; DNA-Binding Proteins - metabolism; Erythroid Cells - metabolism; GATA1 Transcription Factor - genetics; GATA1 Transcription Factor - metabolism; Gene Expression Regulation; Globins - genetics; Globins - metabolism; Humans; Immunoblotting; Immunoprecipitation; Kinetics; LIM Domain Proteins; Locus Control Region; Metalloproteins - genetics; Metalloproteins - metabolism; Promoter Regions, Genetic; Proto-Oncogene Proteins - genetics; Proto-Oncogene Proteins - metabolism; Regulatory Sequences, Nucleic Acid; RNA Polymerase II - metabolism; RNA, Small Interfering - pharmacology; T-Cell Acute Lymphocytic Leukemia Protein 1; Transcription Factors; Transcription, Genetic; Transcriptional Activation; Tumor Cells, Cultured
• ISSN: 1097-2765; 1097-4164
• DOI: 10.1016/j.molcel.2007.09.025

Long-range interactions between distant regulatory elements, such as enhancers, and their target genes underlie the specificity of gene expression in many developmentally regulated gene families. NLI/Ldb1, a widely expressed nuclear factor, is a potential mediator of long-range interactions. Here, we show that NLI/Ldb1 and erythroid-binding partners GATA-1/SCL/LMO2 bind in vivo to the β-globin locus control region (LCR). The C-terminal LIM interaction domain of NLI is required for formation of the complex on chromatin. Loss of the LIM domain converts NLI into a dominant-negative inhibitor of globin gene expression, and knockdown of NLI by using shRNA results in failure to activate β-globin expression. Kinetic studies reveal that the NLI/GATA-1/SCL/LMO2 complex is detected at the β-globin promoter coincident with RNA Pol II recruitment, β-globin transcription, and chromatin loop formation during erythroid differentiation, providing evidence that NLI facilitates long-range gene activation.