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With the emergence of the histone code as a key determinant in the regulation of gene expression, it has been important to develop tools that can not only identify the types and locations of myriad modifications, but also determine how the levels of these modifications change as a result of various processes in a cell. Mass spectrometry has become a method of choice for the investigation of post-translational...
To achieve its full biological activity, NF-κB must undergo a variety of post-translational modifications, including acetylation. Acetylation plays a prominent role in regulating the nuclear action of NF-κB. The RelA subunit of NF-κB forms the major target of acetylation at several different sites. Acetylation of discrete lysine residues in RelA modulates distinct functions of NF-κB, including transcriptional...
The impact of histone phosphorylation, acetylation, and methylation onto transcription and various other cellular DNA-mediated processes is now well established. Numerous histone modification marks, specific sites carrying particular post-translational modifications, have been described and analyzed in detail. Whereas, many methods for the study of histone post-translational modifications involve...
We describe a microplate-based assay for NAD-dependent Class III histone deacetylases (also known as SIRTs) that measures the enzyme-catalyzed release of nicotinamide from radiolabeled NAD, using a boronic acid resin to selectively capture the NAD. This method avoids the need for fluorogenic or radiolabeled peptides or separation of the reaction products using solvent extraction. The protocol reported...
Class III histone deacetylases, or sirtuins, are homologous to the Saccharomyces cerevisiae transcriptional regulator SIR2. The class III enzymes are characterized by their dependence on nicotinamide adenine dinucleotide (NAD + ). This cofactor serves as an acetyl-group acceptor in the deacetylation reaction generating O-acetyl-ADP-ribose. Enzymatic activity of sirtuin can be measured in vitro...
Protein/histone acetyltransferases (PATs/HATs) have been implicated in a number of cellular functions including gene regulation, DNA synthesis, and repair. This paper reviews methods that can be used to quantitatively determine the activity and ultimately the catalytic/kinetic mechanism of PAT/HATs in vitro. Two methods will be described in detail. The first method is a filter-binding assay that measures...
Until recently, identifying the specificities of enzymes that post-translationally modify core histones was performed in vitro using synthetic peptides, purified mononucleosomes or short nucleosome arrays. Unfortunately, the variable results obtained for identical enzymes are often dependent on the in vitro conditions employed. These results are consistent with the conclusion that the manner in which...
The uses of tandem and Fourier transform mass spectrometric methodologies for assignment of the posttranslational sites and occupancies of histones and their isoforms is described employing several illustrative examples. A comparison of information that can be obtained from intact protein sequencing and proteolytic digestion is presented.
Acetyltransferase enzymes target specific lysine residues in substrate proteins. While the list of histone and nonhistone substrates is growing, the mechanisms of substrate selection remain unclear. Here, we describe a mass spectrometric approach to examine the site selection of the acetyltransferase p300 in the HIV-1 protein Tat. Tat is acetylated by p300 at a single lysine (K50) within its basic...
Histone deacetylases are important regulators of transcription and an emerging target for anticancer drugs. We present an overview over various assay formats that include radiolabelled histones, oligopeptides, and small molecules as substrates. The advantages and disadvantages of the various formats in terms of, e.g., substrate availability, throughput or subtype selectivity are discussed. Detailed...
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