ROLE OF HISTONES IN RESTRICTION OF CHROMATIN ACTIVITY IN SUCCESSIVE STAGES OF DEVELOPMENT OF ANTHERIDIAL FILAMENTS OF CHARA-VULGARIS L

  • 1 January 1977
    • journal article
    • research article
    • Vol. 15  (2) , 109-+
Abstract
The binding of 3H actinomycin D(3H AMD) was studied autoradiographically and the extinction following Feulgen''s reaction at short (5 min) hydrolysis in 1N HCl was investigated cytophotometrically in 4 successive (4, 8, 16 and 32 cell) generations of synchronously dividing antheridial filaments of C. vulgaris L. Four stages of interphase, i.e., early and late S and early and late G2, were taken into consideration in each generation. The intensity of 3H AMD binding, except for early S, declines gradually in successive generations, i.e., in the developmental stages of antheridial filaments. Each generation reveals the highest radioactivity in the cells of early G2. Removal of lysine-rich histones in late G2 is the more effective for enhancing 3H AMD binding the more advanced is the stage of development of antheridial filaments. In early phase S extraction of arginine- or lysine-rich histones stimulates the binding of 3H AMD in the same degree. When all histones are removed, differences in the intensity of 3H AMD binding between particular generations of antheridial filaments disappear altogether. After a 5 min hydrolysis Feulgen''s reaction reveals mainly loose chromatin, whereas after 16 min compact chromatin predominates. Removal of lysine-rich histones brings about an increased extinction after a 5 min hydrolysis in all phases of the cell cycle and in all developmental stages of antheridial filaments. After 5 min of hydrolysis, the extinction value per nuclear area in all experimental series, despite identical DNA contet, undergoes a gradual reduction with diminishing nuclear volume in the successive generations of antheridial filaments. This reduction is correlated with a decreased intensity of 3H AMD binding. Apparently a decline in chromatin activity in successive developmental stages of antheridial filaments of C. vulgaris L. is caused by the progressing condensation of chromatin for which lysine-rich histones are responsible.