DNA-REPLICATION OCCURS AT THE NUCLEAR MATRIX

Chromatin in eukaryotic cells is partitioned into loop-domains by bind ing of MARs to the nuclear matrix. It is increasingly accepted that th e replication event is attached to the nuclear matrix. In this study, chicken myelomonocytic HD11 cells were synchronized at the G1/S phase boundary, and after release into the S phase, were immediately pulse-l abelled with 5-bromodeoxyuridine (BrdU). The chromatin was then fracti onated into the nuclear matrix and a solubilized fraction to determine the partitioning of BrdU in newly replicated DNA. Me found that in ea rly S phase-synchronized cells newly replicated DNA was highly enriche d in the nuclear matrix. This result indicates that origins of DNA rep lication in eukaryotic cells are attached at the nuclear matrix.