Vol. 97, No. 4, 1980 December 31, 1980 BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS Pages 1541-1547 DNA POLYMERASE ~ IS TIGHTLy BOUNDTO THE NUCLEAR MATRIX OF ACTIVELY REPLICATING LIVER Harold C. Smith and Ronald Berezney Division of Cell and Molecular Biology Department of Biological Sciences State University of New York Buffalo, New York 14260 Received November 4, 1980 SUMMARY Nuclear matrices from actively replicating regenerating liver contain significant DNA polymerase ~ activity but only trace amounts of ~ polymerase. In contrast, normal liver matrices are essentially devoid of ~ polymerase. The matrix bound ~ polymerase is completely inhibited by N-ethylmaleimide and aphidocolin but not by dideoxy TTP. We propose that functional replicational complexes are assembled dynamically on the nuclear matrix during active DNA replication. INTRODUCTION Previous findings (I-6) have demonstrated a close association of in vivo replicating DNA with the nuclear matrix, a residual nucleoskeletal structure isolated and characterized from a variety of eukaryotic cells (7). These results suggested that the sites of DNA replication are close to or actually bound to the nuclear matrix (4-6, 8). The putative matrix bound complexes presumably would contain the appropriate enzymes and other factors involved in replication. The aforementioned considerations have prompted us to investigate the possible association of functional replicational complexes with isolated nuclear matrices. In this communication we report a greatly enhanced associ- ation of DNA polymerase ~, which is believed generally to be a true replica- tive enzyme (9), with nuclear matrices isolated from actively replicating Abbreviations used: NEM, N-ethylmaleimide; PHMB, p-hydroxymercuribenzoate; dNTP(s); deoxynucleoside triphosphate(s); dideoxy TTP, 2',3' dideoxythymidine triphosphate; LS buffer, 0.2 mM MgCI 2, I0 mM Tris pH 7.4 (23°C); HS buffer, 2 M NaCl, 0.2 mM MgCI 2, I0 mM Tris pH 7.4 (23oc). 1541 0006-291X/80/241541-07501.00/0 Copyright © 1980 by Academic Press, Inc. All rights of reproduction in any form reserved.