DISTINCTIVE FEATURES OF DINOFLAGELLATE CHROMATIN - ABSENCE OF NUCLEOSOMES IN A PRIMITIVE SPECIES PROROCENTRUM-MICANS E

  • 1 January 1981
    • journal article
    • research article
    • Vol. 23  (2) , 295-302
Abstract
The absence of nucleosome-like structures from purified nuclei of the primitive dinoflagellate P. micans was demonstrated by 3 means. EM revealed mostly thin, smooth 6 nm nucleofilaments in chromatin incubated at various ionic strengths and either fixed in 0.1% glutaraldehyde or unfixed. No beads-on-a-string structure was found. Analysis of nuclear proteins showed that low amounts of basic proteins were present (basic proteins: DNA < 0.1), the 2 major ones with MW 12,000 and 13,000 and that histones characteristic of eukaryotes were absent. Digestion of the nuclei with micrococcal endonuclease or DNase I did not result in partially digested DNA fragment repeats. Only about 10% of the bulk of the nuclear DNA was digested by micrococcal endonuclease. The high MW of the remainder suggests particular protection against this type of nuclease. The evolutionary position of the dinoflagellate protists with respect to the prokaryotes and eukaryotes was discussed.