Abstract
SUMMARY: A soluble protein extract, obtained after35S labeling exponential cultures ofCryptothecodinium cohniifor 4–5 generations, was fractionated on DNA‐cellulose. The protein eluted at high salt concentrations from this homologous DNA‐containing matrix was then separated, by chromatography on BioGel P150 and P200 sieve gels. Two prominent chromatographic species of 22,000 and 35,000 daltons plus a substantial amount of material in the molecular weight range of 80,000–140,000 were resolved. The application of this analytical procedure to the study of transcriptional control in the cell cycle is discussed.