Chromatin remodeling by cell cycle stage-specific extracts from Physarum polycephalum

Remodeling of chromatin is an essential process allowing the establishment of specific genetic programs, The slime mold Physarum polycephalum presents the attractive advantage of natural synchrony of the cell cycle in several million nuclei, Whole-cell extracts prepared at precise stages during the cell cycle were tested for the ability to induce remodeling in erythrocyte nuclei as monitored bg microscopy; protamine competition assays, micrococca l nuclease digestions, and release of histone H5. Extracts derived from two specific cell cycle stages caused opposite types of changes in erythrocyte nuclei, An increase in chromatin compaction was imparted by extracts prepa red during S-phase while extracts harvested at the end of G2-phase caused i ncreases in nuclear volume, DNA accessibility, and release of linker histon e, We also found that late G2 extracts had the ability to alter the DNase I digestion profile of mononucleosomes reconstituted in vitro in a classical nucleosome remodeling assay, The relevance of these finding to the Physaru m cell cycle is discussed.