Reassembly of C-myc and relaxation of C-fos nucleosomes during differentiation of human leukemic (HL-60) cells

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

“…Adoption of a n inactive chromatin conformation (Chou et al, 1986) by the c-myc gene may be accompanied by changes in either the sequences which function as a MAR or by a n altered affinity of the myc-MAR for the NM. Our previous work indicated that the myc gene region which functions as a MAR is not exchanged for another region during phorbol-ester treatment (Chou et al, 1990).…”

“…The low-abundance NM proteins from cell lines derived from diverse tissues show qualitative differences in their composition when analyzed by two-dimensional polyacrylamide gel electrophoresis (Fey and Penman, 1988). The increased retention of the myc-MAR by NM from PMAinduced HL-60 cells thus may result from the same mechanisms that result in the chromatin structural alterations that accompany phorbol-ester induction of HL-60 cell differentiation (Grosso and Pitot, 1985;Chou et al, 1986).…”

“…Phorbol ester induction of monocytic differentiation of HL-60 cells (PMA HL-60 cells) is accompanied by changes in myc chromatin structure (Gross0 and Pitot, 1985) and the rearrangement of nucleosomal subunits (Chou et al, 1986). Adoption of a n inactive chromatin conformation (Chou et al, 1986) by the c-myc gene may be accompanied by changes in either the sequences which function as a MAR or by a n altered affinity of the myc-MAR for the NM. Our previous work indicated that the myc gene region which functions as a MAR is not exchanged for another region during phorbol-ester treatment (Chou et al, 1990).…”

“…Differentiation along either pathway is accompanied by suppression of c-myc expression and cessation of cell proliferation. Suppression of c-myc expression is associated with changes of myc chromatin structure (Siebenlist et al, 1984;Grosso and Pitot, 1985) and rearrangement of nucleosoma1 subunits (Chou et al, 1986). We have recently found a MAR of the c-myc protooncogene to reside within a 1.4-kb region between the Cla I and Eco RI restriction sites at the 3'-end of the gene (Chou et al, 1990).…”

The role of protein phosphorylation in the control of cell growth and differentiation

“…Topoisomerase I and II are both phosphoproteins whose activity is regulated by phosphorylation (Durban et al, 1983;Ackerman et al, 1985). By altering DNA structure, topoisomerases may play a role in the assembly and relaxation of nucleosomes, such as c-myc and c-fos, respectively, which occurs during HL60 cell differentiation (Chou et al, 1986). Of particular interest are reports in the literature that PKA binds directly to DNA (Shabb & Miller, 1986) and that the regulatory subunit of PKA has topoisomerase I activity (Constantinou et al, 1985).…”