The 5‘ Boundary of the Human Apolipoprotein B Chromatin Domain in Intestinal Cells

• Published in: Biochemistry (Easton) 2001-06, Vol.40 (23), p.6731-6742
• Main Authors: Antes, Travis J, Namciu, Stephanie J, Fournier, R. E. K, Levy-Wilson, Beatriz
• Format: Article
• Language: English
• Subjects: 5' Untranslated Regions - chemistry; 5' Untranslated Regions - genetics; Animals; Apolipoproteins B - chemistry; Apolipoproteins B - genetics; Base Composition; Binding Sites - genetics; Caco-2 Cells - chemistry; Caco-2 Cells - metabolism; CCCTC-Binding Factor; Chromatin - chemistry; Chromatin - genetics; COS Cells; Deoxyribonuclease EcoRI - genetics; DNA-Binding Proteins - genetics; DNA-Binding Proteins - metabolism; Drosophila melanogaster; Drosophila melanogaster - genetics; Drosophila Proteins; Enhancer Elements, Genetic; Female; Humans; matrix attachment regions; Nuclear Matrix - genetics; Nuclear Matrix - metabolism; Nuclear Proteins; Protein Structure, Tertiary - genetics; Repressor Proteins - antagonists & inhibitors; Repressor Proteins - genetics; Repressor Proteins - metabolism; RNA-Binding Proteins - genetics; Transcription Factors - genetics; Transcription Factors - metabolism; transgenes
• ISSN: 0006-2960; 1520-4995
• DOI: 10.1021/bi0100743

The 5‘ boundary of the chromosomal domain of the human apolipoprotein B (apoB) gene in intestinal cells has been localized and characterized. It is composed of two kinds of boundary elements; the first, functional boundary is an insulator activity exhibited by a 1.8 kb DNA fragment located between −58 and −56 kb upstream of the human apoB promoter. In this region, an enhancer-blocking activity has been mapped to a CTCF binding site that is located upstream of two apoB intestinal enhancers (IEs), the 315 IE and the 485 IE. The CTCF site represents a boundary between two types of chromatin structure:  an open, DNaseI-sensitive region 3‘ of the CTCF site containing the intestinal regulatory elements and a closed, DNaseI-resistant region 5‘ of the CTCF site. The 1.8 kb fragment harboring the CTCF site also insulated mini-white transgenes against position effects in Drosophila melanogaster. The second, structural boundary is represented by a nuclear matrix attachment region (MAR), situated about 3 kb 5‘ of the CTCF site. This MAR may represent the 5‘ anchorage site for a chromosomal loop that functions to bring the intestinal regulatory elements closer to the apoB promoter.