| Abstract: | Summary— Employing several antibodies to phosphorylated protein epitopes, we demonstrate by immunostaining that the macronuclear replication band (RB) of the ciliated protozoan Euplotes eurystomus contains a high concentration of phosphoproteins. Enrichment is principally within the rear zone of the RB, the region of DNA synthesis and chromatin assembly. By immunoblot analysis, the various antibodies reacted with a diversity of macronuclear phosphoproteins, one of which was phosphorylated histone Hl. This diversity of phosphoproteins was also supported by examination of the macronuclear matrix generated by high NaCl extraction. Available evidence clearly indicates that the ultrastructural wave of chromatin modulation accompanying DNA replication is spatially correlated with a wave of localized nuclear protein phosphorylation. |
