English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

We have studied the pathway of nuclear assembly from demembranated sperm chromatin by fractionating a cell-free system from Xenopus eggs (Lohka, M. J., and Y. Masui. 1983. Science (Wash. DC). 220:719-721). Both the soluble fraction and a washed vesicular fraction are required for formation of normal nuclei that initiate replication in vitro. The soluble fraction alone decondenses chromatin and the vesicular fraction alone surrounds chromatin with membranes. Both fractions are required for formation of nuclear pore complexes. Recombining these two fractions recovers approximately 100% of the nuclear assembly and DNA replication activities. Restricting the proportion of the vesicular fraction slows acquisition of the nuclear membrane and allows observation of immature nuclear pores ("prepores"). These form as arrays around and within the chromatin mass before membranes form. Subsequently membrane vesicles bind to these prepores, linking them by a single membrane throughout the chromatin mass. At the periphery this single membrane is surrounded by an outer membrane. In mature nuclei all membranes are at the periphery, the two membranes are linked by pores, and no prepores are seen. Nuclear assembly and replication are inhibited by preincubating the chromatin with the vesicular fraction. However nuclear assembly is accelerated by preincubating the condensed chromatin with the soluble fraction. This also decreases the lag before DNA replication. Initiation of DNA replication is only observed after normal nuclei have fully reassembled, increasing the evidence that replication depends on nuclear structure. The pathway of nuclear assembly and its relationship to DNA replication are discussed.

Steps in the assembly of replication-competent nuclei in a cell-free system from Xenopus eggs.