Characterization of the chicken beta-globin insulator

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 94; no. 2; pp. 575 - 580
• Main Authors: Chung, J.H. (National Institutes of Health, Bethesda, MD.), Bell, A.C, Felsenfeld, G
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences of the United States of America 21.01.1997; National Acad Sciences; National Academy of Sciences
• Subjects: ADN; ADN RECOMBINADO; ADN RECOMBINE; Animals; Base Composition; Base Sequence; Binding sites; Biological Sciences; Chickens - genetics; Cloning, Molecular; Deoxyribonuclease I - metabolism; Deoxyribonucleic acid; DNA; DNA Footprinting; DNA Methylation; Drosophila; Enzymes; GENE; Gene Expression Regulation; GENES; Genetic loci; Genetics; Globins - genetics; HISTONAS; HISTONE; K562 cells; Methylation; Molecular Sequence Data; OXIDORREDUCTASAS; OXYDOREDUCTASE; Plasmids; POLLO; POULET; Poultry; Promoter regions; Promoter Regions, Genetic; PROTEINAS AGLUTINANTES; PROTEINE DE LIAISON; Regulatory Sequences, Nucleic Acid; Reporter genes; SECUENCIA NUCLEOTIDICA; SEQUENCE NUCLEOTIDIQUE
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.94.2.575

Insulators, first identified in Drosophila, are DNA sequence elements that shield a promoter from nearby regulatory elements. We have previously reported that a DNA sequence at the 5' end of the chicken beta-globin locus can function as an insulator. It is capable of shielding a reporter gene from the activating effects of a nearby mouse beta-globin locus control region element in the human erythroleukemic cell line K562. In this report, we show that most of the insulating activity lies in a 250-bp CpG island (core element), which contains the constitutive DNase I-hypersensitive site (5'HS4). DNA binding assays with the core sequence reveal a complex protein binding pattern. The insulating activity of the core element is multiplied when tandem copies are used. Although CpG islands are often associated with promoters of housekeeping genes, we find little evidence that the core element is a promoter. Furthermore, the insulator differs from a promoter in its ability to block the locus control region effect directionally