Work in the authors' laboratory is supported by a grant from the National Institute of General Medical Sciences (GM41628) and by a grant to the Stowers Institute for Medical Research from the Helen Nelson Medical Research Fund at the Greater Kansas City Community Foundation.

1. ATP-dependent Nucleosome Remodeling Assays
To measure ATP-dependent nucleosome remodeling activities, immunopurified INO80 or INO80 subcomplexes are incubated with ATP and a mononucleosomal substrate, which contains a single nucleosome positioned at one end of a 216-bp, 32P-labeled DNA fragment. The reaction products are then subjected to electrophoresis in native poly-acrylamide gels.
<ol>
	<li>To generate the 32P-labeled, &#39;601&#39; DNA fragment, amplify from pG...

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The authors declare that they have no competing financial interests.

To ensure that nucleosome remodeling and ATPase activities we observe in assays depend on the catalytic activity of INO80 complexes, and not on contaminating remodeling and/or ATPase enzymes, we routinely assay nucleosome remodeling and ATPase activity of catalytically inactive versions of INO80 complexes, purified in parallel with wild type INO80 using the same procedure. A negative control reaction lacking ATP should also be performed when assaying nucleosome remodeling activity to test for the presence of contaminatin...

SNF2 family chromatin remodeling complexes include a central SNF2-like ATPase subunit 1,2. Some SNF2-like ATPases function as single subunit enzymes, while others function as the catalytic subunit of larger multi-subunit complexes. Elucidating the molecular mechanisms by which each of the subunits of chromatin remodeling complexes contribute to their activities requires the ability to perform biochemical assays that dissect the remodeling process.
ATP-dependent nucleosome remodeling by the human INO80 complex and other chromatin remodeling enzymes can be envisioned as a multi-step process that starts with binding of the remodeling enzyme to nucleosomes, followed by activation of its DNA- and/or nucleosome-dependent ATPase, translocation of the remodeling enzyme on nucleosomal DNA, and eventual repositioning of nucleosomes 1,2. Understanding the molecular details of the ATP-dependent chromatin remodeling process requires dissection of the remodeling reaction into its individual steps and definition of the contributions of individual subunits of the chromatin remodeling complex to each step of the reaction. Such analyses require the ability to analyze nucleosome remodeling and other activities using defined molecular substrates in vitro.
In a previous JOVE protocol, we described procedures used to generate INO80 chromatin remodeling complexes and subcomplexes with defined subunit compositions 3. Here, we present three biochemical assays that enable quantitative analysis of the nucleosome binding, DNA- and nucleosome-activated ATPase, and nucleosome remodeling activities associated with such complexes.

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biochemical assays for analyzing activities of atp-dependent chromatin remodeling enzymes

Members of the SNF2 family of ATPases often function as components of multi-subunit chromatin remodeling complexes that regulate nucleosome dynamics and DNA accessibility by catalyzing ATP-dependent nucleosome remodeling. Biochemically dissecting the contributions of individual subunits of such complexes to the multi-step ATP-dependent chromatin remodeling reaction requires the use of assays that monitor the production of reaction products and measure the formation of reaction intermediates. This JOVE protocol describes assays that allow one to measure the biochemical activities of chromatin remodeling complexes or subcomplexes containing various combinations of subunits. Chromatin remodeling is measured using an ATP-dependent nucleosome sliding assay, which monitors the movement of a nucleosome on a DNA molecule using an electrophoretic mobility shift assay (EMSA)-based method. Nucleosome binding activity is measured by monitoring the formation of remodeling complex-bound mononucleosomes using a similar EMSA-based method, and DNA- or nucleosome-dependent ATPase activity is assayed using thin layer chromatography (TLC) to measure the rate of conversion of ATP to ADP and phosphate in the presence of either DNA or nucleosomes. Using these assays, one can examine the functions of subunits of a chromatin remodeling complex by comparing the activities of the complete complex to those lacking one or more subunits. The human INO80 chromatin remodeling complex is used as an example; however, the methods described here can be adapted to the study of other chromatin remodeling complexes.

The figures show representative results of biochemical assays used to characterize INO80 activities, including nucleosome sliding (Figure 1) and binding (Figure 2) assays and DNA- or nucleosome-dependent ATPase assays (Figure 3).
The experiment shown in Figure 1 compares the ability of intact INO80 complexes purified through FLAG-Ies2 or FLAG-INO80E and of INO80 subcomplexes purified through either FLAG-Ino80&#916;N or Ino80&#...

Watch this Scientific Journal Video about Biochemical Assays for Analyzing Activities of ATP-dependent Chromatin Remodeling Enzymes at JoVE.com

Biochemical Assays for Analyzing Activities of ATP-dependent Chromatin Remodeling Enzymes

Here we describe biochemical assays that can be used to characterize ATP-dependent chromatin remodeling enzymes for their abilities to 1) catalyze ATP-dependent nucleosome sliding, 2) engage with nucleosome substrates, and 3) hydrolyze ATP in a nucleosome- or DNA-dependent manner.

Members of the SNF2 family of ATPases often function as components of multi-subunit chromatin remodeling complexes that regulate nucleosome dynamics and ...

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14.7K visualizações.  Stowers Institute for Medical Research. Here we describe biochemical assays that can be used to characterize ATP-dependent chromatin remodeling enzymes for their abilities to 1) catalyze ATP-dependent nucleosome sliding, 2) engage with nucleosome substrates, and 3) hydrolyze ATP in a nucleosome- or DNA-dependent manner.