[UV-light-tested protein--DNA interactions in the nuclei during the cell cycle in Physarum polycephalum]

The release of DNAs from nuclear preparations isolated at different steps of the cell cycle of the synchronous culture of Physarum polycephalum and irradiated with UV-light for 5 min (lambda 253.7 A, i = 1.8 . 10(2) j . m-2 . min-1) into 1% Na-DS - 1.5 M NaCl solution was studied. The value obtained correlated well with the degree of binding of interacting proteins with DNA in chromatin and was identical for all the preparations tested with the only exception of the nuclei isolated at the end of the S-phase, when a slight but significant (15 +/- 10%) increase in DNA release was observed. The results obtained are discussed in terms of structural transitions and function of chromatin during the cell cycle of the myxomycete Physarum polycephalum.