Abstract
Nuclei isolated from Tetrahymena pyriformis were subfraction-ated by treating them with micrococcal nuclease followed by successive centri-fugations. In the pellet (Lp) obtained by the first centrifugation (low speed), 80-94 % of the nuclear DNA was recovered. The pellet (Hp) and the super-natant (Hs) obtained by the second centrifugation (high speed) contained 2-10 % and 4-10 % of the nuclear DNA, respectively. The profiles of sucrose density gradient centrifugation and electrophoresis on polyacrylamide gel indicated that fraction Hs consists of mono- to oligonucleosomes. The RNA polymerase activity of fraction Hp was sensitive to α-amanitin, which suggests that the fraction contains the transcriptionally active region of chromatin. Poly(A) polymerase activity was demonstrated in all three fractions, but the specific activities (both per DNA and per protein) were high in fractions Hp and Hs.
