Vol. 157, No. 2,1988 December15, 1988 BIOCHEMICALAND BIOPHYSICALRESEARCHCOMMUNICATIONS Pages 500-506 LOCATIONANDMETHYLATION PATTERN OF A NUCLEARMATRIXASSOCIATED REGION IN THE HUMAN PROa2(I) COLLAGENGENE G.C. Ellis, A.F. Grobler-Rabie, F.S. Hough and A.J. Bester Department of Internal Medicine, Endocrinology Division and MRC Research Centre for Molecular and Cellular Biology, University of Stellenbosch Medical School, Tygerberg, 7505, South Africa Received October 7, 1988 SUMMARY Using both a 25mMLithium di-iodosalicylic acid (LIS) and a 2M NaCl extraction procedure to extract nuclear matrices from white cells we have identified a O.9kb nuclear matrix associated region (MAR) in the human proa2(1) collagen gene. The MAR is located towards the 3' coding end of the gene, it is completely associated with the matrix in transcriptionally inactive white cells but is incompletely associated with the matrix in transcriptionally active fibroblasts. Futhermore the methylation state of the fibroblast gene in the region coinciding with the MAR showed unique differences when compared to adjacent sites in the fibroblast gene and corresponding sites of the white cell gene. ©1988 Academic Press,lnc. One level of the spatial organisation of chromatin in interphase nuclei is represented by the arrangement of DNA into chromatin loop domains (1,2), the bases of which are anchored to the nuclear matrix at specific sites known as matrix (or scaffold) association regions (MARs or SARs) (3,4). Using in vitro and/or in vivo approaches MARshave been identified adjacent to a series of Drosophila genes (3,5,6), within the mouse heavy chain immunoglobulin locus (4,7), in ribosomal RNA genes (8) and in the rat 2-macroglobulin gene (9). They appear to represent a family of homologous sequences which play a role in gene expression and may be a factor in determining the phenotypic expres- sion of the cell (10). Various procedures have been used to isolate the nuclear substructures (11) and in this study we used both a 25mMLIS and a 2M NaCl extraction procedure to investigate the organisation of the 3' end of the human proa2(I) collagen gene on the nuclear matrix. In contrast to 2M NaCl the LIS extraction procedure has been reported to maintain the fidelity of the matrix-DNA interactions (5). Human proa2(I)collagen gene is a 35kb pair single copy gene located on chromosome 7, the transcription unit contains 52 exons which code for the a2(I) chain of the Type I procollagen heterotrimer (]2-]4). The collagen genes show stage- and tissue-specific gene expression (]5-]8), and regulatory 0006-291X/88 $1.50 Copyright © 1988 by Academic Press, Inc. All rights of reproduction in any form reserved. 500