Sequence-specific binding of a c-myc nuclear-matrix-associated region shows increased nuclear matrix retention after leukemic cell (HL-60) differentiation

✍ Scribed by Chou, Robin H. ;Churchill, Judy Rae ;Mapstone, Diane E. ;Flubacher, Marcella M.

• Publisher: Wiley (John Wiley & Sons)
• Year: 1991
• Tongue: English
• Weight: 914 KB
• Volume: 191
• Category: Article
• ISSN: 0002-9106
• DOI: 10.1002/aja.1001910311

✦ Synopsis

HL-60 cells, a human promyelocytic leukemia cell line, contain amplified c-myc DNA sequences and mRNA transcripts. These cells can be induced to undergo macrophage differentiation by phorbol esters, which results in suppression of c-myc expression and cessation of cell proliferation. The nuclear matrix (NM), a nuclear skeleton resistant to DNase I digestion and high salt extraction, is proposed to be involved in DNA replication, gene regulation, and the correct distribution of DNA at mitosis. We have previously identified a nuclear-matrix-associated region (MAR) of the c-myc protooncogene to reside in a 1.4-kb region between Cla I and Eco RI restriction sites at the 3'-end of the gene. A 172-bp Dra IlDra I subfragment of the 1.4-kb region was shown to be a major component of the MAR (myc-MAR), and this subfragment was demonstrated to be recognized by a nuclear protein (~25). In this report we demonstrate that +X174 DNA, or the synthetic copolymers poly[d(G-C)] and poly[d(A-T)], are not effective suppressors of the binding of the myc-MAR to isolated NM, indicating that the binding sequence(s1 are unique. We find that the addition of partially purified protein p25 increases the relative affinity of the myc-MAR for HL-60 NM in an in vitro assay system. NM isolated from HL-60 macrophages induced by phorbol esters retains significantly more myc-MAR DNA fragment in the presence of an excess amount of competitor DNA than does NM from untreated HL-60 cells. These data suggest that a change of the myc-MAR association with the NM occurs after monocytic differentiation of HL-60 cells.