J. Svaren et al., ANALYSIS OF THE COMPETITION BETWEEN NUCLEOSOME FORMATION AND TRANSCRIPTION FACTOR-BINDING, The Journal of biological chemistry, 269(12), 1994, pp. 9335-9344
We have studied the competitive binding of histones and the Rous sarco
ma virus internal enhancer binding factor (IBF) factor (which recent s
tudies indicate is almost certainly cEBP beta). We find that histones
and IBF are incapable of forming a ternary complex with a 159- base pa
ir (bp) fragment of DNA containing a single IBF binding site and that
histones and factor are mutually exclusive in binding. We have analyze
d the various physical parameters of binding, in an attempt to underst
and how the factor might establish an exclusive binding in the cell. T
he stability of the nucleosome and the factor-DNA complex have been de
termined, and in addition a minimum value for the affinity of the hist
one octamer has been computed. We find that in simple competition the
IBF can successfully compete, only if the substrate DNA is shorter tha
n 140 bp. The relevance of these results is discussed in terms of a ki
netic model for successful factor competition during the replication o
f the factor binding site in the cell.