Isolation and partial characterization of dinoflagellate chromatin

Abstract

Chromatin was prepared by two different methods from isolated nuclei of Gyrodinium cohnii ( Cryptothecodinium cohnii) and Peridinium trochoideum. These isolation procedures are different from those generally used to prepare eukaryote chromatin, because the latter do not work for dinoflagellate chromatin. The chemical composition of this chromatin is similar for both methods of preparation and both organisms. Dinoflagellate chromatin contains DNA, RNA, acid-soluble and acid-insoluble protein as does chromatin from higher plants and animals, but the amount of acid-soluble protein relative to DNA (0.02–0.08) is much lower than that of typical eukaryotes (about 1). Evidence is presented to show that proteolytic degradation is unlikely to account for the low acid-soluble protein content in dinoflagellate chromatin. Exclusion chromatography of the chromatin on large-pore gels (Bio Gel A-15m or Sephadex G-200) indicates that the bulk of the protein present in the chromatin preparations migrates with the DNA. G. cohnii and P. trochoideum chromatin show an ultraviolet absorption spectrum, which is intermediate between DNA and typical eukaryote chromatin, and this is not significantly changed by gel exclusion chromatography. Preliminary results suggest that the dinoflagellate DNA-associated proteins do not stabilize the DNA against melting. Chromatin prepared from log-phase cells has more protein and RNA than chromatin from stationary-phase cells. The chemical composition of dinoflagellate chromatin is compared with that of prokaryotes and eukaryotes.