Assembly of spaced chromatin involvement of ATP and DNA topoisomerase activity.

摘要: Undiluted extracts from eggs or oocytes of Xenopus laevis support the assembly chromatin with physiologically spaced nucleosomes. Micrococcal nuclease and DNase I digestion experiments show that nucleosome formation as well supercoiling circular DNA concomitant to do not require ATP Mg2+. However these factors are essential for stability physiological spacing assembled chromatin. gamma-S-ATP can substitute in this process. With topoisomers defined linking number topological interconversions proceed by steps unity, both vitro vivo, indicating topoisomerase is dominantly acting Novobiocin sensitivity occurred only diluted was unrelated an inhibition II. Finally, occurs efficiently on linear although less stable than DNA. From results we propose mature formed a two-step reaction. In first step, deposition independently Thus, be uncoupled their spacing. activity involved relaxation constraints generated rather process itself. The second requiring Mg2+, generates properly