Related Experiment Video

Updated: Aug 7, 2026

In Vitro Nuclear Assembly Using Fractionated Xenopus Egg Extracts
04:49

In Vitro Nuclear Assembly Using Fractionated Xenopus Egg Extracts

Published on: September 2, 2008

Mechanism of chromatin assembly in Xenopus oocytes

I Ruberti, A Worcel

    Journal of Molecular Biology
    |June 5, 1986
    PubMed

    Insights

    Researchers studied chromatin assembly using Xenopus oocyte extract. They found a complex containing histone precursors that gradually forms supercoiled nucleosomal chromatin, requiring ATP.

    Area of Science:

    • Molecular Biology
    • Chromatin Biology
    • Developmental Biology

    Background:

    • Chromatin assembly is a fundamental process for DNA packaging in eukaryotes.
    • Xenopus oocyte extract provides a rich system for studying early events in chromatin formation.

    Purpose of the Study:

    • To analyze the mechanism of chromatin assembly catalyzed by Xenopus oocyte extract (S-150).
    • To identify the components and pathway involved in the formation of nucleosomal chromatin.

    Main Methods:

    • Analysis of a 50 S complex formed from pUC DNA and S-150 extract.
    • Micrococcal nuclease digestion to characterize subnucleosomal particles.
    • In vitro supercoiling assays to study chromatin formation dynamics.
    • Investigation of ATP requirement and inhibition by novobiocin.

    Main Results:

    • A 50 S complex containing relaxed DNA and protein precursors is formed.
    • This complex generates subnucleosomal 7 S particles upon nuclease digestion.
    • The complex gradually supercoils into nucleosomal chromatin, requiring ATP and involving mature histones H3 and H4.
    • Isolated complexes can supercoil in vitro, indicating they contain necessary assembly factors.

    Conclusions:

    • The Xenopus S-150 extract contains a pre-assembly complex with histone precursors and enzymes for chromatin formation.
    • Chromatin assembly proceeds via a stepwise pathway involving supercoiling and histone incorporation.
    • This system offers insights into the fundamental mechanisms of nucleosome formation and DNA packaging.

    More Related Videos

    A Cell Free Assay to Study Chromatin Decondensation at the End of Mitosis11:04

    A Cell Free Assay to Study Chromatin Decondensation at the End of Mitosis

    Published on: December 19, 2015

    Chromatin Spread Preparations for the Analysis of Mouse Oocyte Progression from Prophase to Metaphase II10:39

    Chromatin Spread Preparations for the Analysis of Mouse Oocyte Progression from Prophase to Metaphase II

    Published on: February 26, 2018

    Related Concept Videos

    Lampbrush Chromosomes01:51

    Lampbrush Chromosomes

    In 1882, Flemming observed lampbrush chromosomes (LBC) in salamander eggs. Later in 1892, Rückert observed LBCs in shark egg cells and coined the term "lampbrush chromosomes" because they looked like brushes used to clean kerosene lamps.
    LBCs are made up of two pairs of conjugating homologous chromatids. Each chromatid consists of alternatively positioned regions of condensed-inactive chromatin and loosely placed-active side loops, which can be contracted and extended. The loops resemble the...
    Inheritance of Chromatin Structures03:17

    Inheritance of Chromatin Structures

    Epigenetics is the study of inherited changes in a cell's phenotype without changing the DNA sequences. It provides a form of memory for the differential gene expression pattern to maintain cell lineage, position-effect variegation, dosage compensation, and maintenance of chromatin structures such as telomeres and centromeres. For example, the structure and location of the centromere on chromosomes are epigenetically inherited. Its functionality is not dictated or ensured by the underlying DNA...
    Euchromatin01:01

    Euchromatin

    The extent of chromatin compaction can be studied by staining chromatin using specific DNA binding dyes. Under the microscope, the dense-compacted regions take up more dye, appearing darker, while the less-compact areas take up less dye and appear lighter. Based on the compaction level, chromatins are classified into two primary forms – euchromatin and heterochromatin.
    Euchromatin is the less dense region of the chromatin and stains lighter. Euchromatin contains histone H3 extensively...
    Duplication of Chromatin Structure02:05

    Duplication of Chromatin Structure

    The process of chromosome duplication during cell division requires genome-wide disruption and re-assembly of chromatin. The chromatin structure must be accurately inherited, reassembled, and maintained in the daughter cells to ensure lineage propagation.
    The basic unit of the chromatin is the nucleosome, consisting of DNA wrapped around octameric histone proteins and short stretches of linker DNA separating individual nucleosomes. The histone proteins within the nucleosome have their...
    Spindle Assembly02:50

    Spindle Assembly

    Spindle assembly occurs through three, often coexisting, pathways – the centrosome-mediated pathway, the chromatin-mediated pathway, and the microtubule-mediated pathway – collectively contributing to form a robust spindle apparatus.
    In most cells, centrosomes are the primary microtubule nucleation centers. In the centrosome-mediated pathway, the G2-prophase transition triggers centrosome maturation and increased microtubule nucleation. Progressive nucleation results in a microtubule array...
    Chromatin Modification in iPS Cells01:32

    Chromatin Modification in iPS Cells

    Chromatin modification alters gene expression; therefore, scientists can add histone-modifying enzymes, histone variants, and chromatin remodeling complexes to somatic cells to aid reprogramming into pluripotent stem (iPS) cells.
    Compact chromatin makes reprogramming difficult. Enzymes, such as histone demethylases and acetyltransferases, are often added during reprogramming to loosen the chromatin, making the DNA more accessible to transcription factors. Molecules that inhibit histone...