In fact, CBP/p300 have been reported to interact with more than 400 different cellular proteins to date 64, including factors important to cancer development and progression such as HIF-1, beta-catenin, c-Myc, c-Myb, CREB, E1, E6, p53, AR, and ER. cancer, and we will discuss the implications of such changes on how patients are assigned to therapeutic agents. Finally, we will explore what the future holds in the design of small molecule inhibitors for modulation of levels or functions of acetylation states. Introduction From transcriptional regulation to metabolic functions, protein acetylation is involved in several processes that keep a cell working properly. Acetylation is a dynamic process that involves the removal of a hydrogen atom on the episilon NH3+ side chain of lysines followed by the transfer of an acetyl group from acetyl-CoA (AcCoA). This exchange neutralizes the positive charge on the lysine and also changes the structure of the R-group on this amino acid, leading to various effects on the protein modified. Lysine acetylation chemically blocks other modifications, such as methylation or ubiquitination, Gosogliptin for example, which can in turn increased protein stability, alter subcellular localization, or change the spectrum of interacting proteins. As such, acetylation provides a rich regulatory switch. Acetylation levels are regulated by a balance in the activities of acetyltransferases and deacetylases. Although originally termed histone acetyltransferases (HATs), due to their actions towards abundant histone substrates, lysine acetyltransferases (KATs) are located both in the nucleus and in the cytoplasm, and they have many non-histone substrates as well. Deacetylases similarly have multiple substrates, but they are still primarily referred to as HDACs rather than KDACs. Several excellent reviews on HDAC families and their functions are available 1C3, so we will focus mostly on acetylation and KATs in this review. Histone Acetylation and Chromatin Regulation PKX1 In the nucleus, DNA is packaged into chromatin. The basic unit of chromatin is the nucleosome, which consists of 146 bp of DNA and histones, the proteins that provide the scaffold that Gosogliptin DNA is wrapped around. Histones contain a globular domain that promotes histone-histone interactions within the nucleosome and also provides a binding surface for DNA. In addition, they contain tail domains that protrude out of the nucleosome, where they influence histone-histone interactions, interactions between histones and DNA, and between histones and other proteins. Although both the globular domains and the tail domains can be modified, the histone tails are particularly rich in modifications, including methylation, acetylation, phosphorylation, ubiquitination, and sumoylation. The many sites and types of modification provide a wealth of variable combinations, which in turn provides huge regulatory potential Gosogliptin for remodeling chromatin states to either facilitate or inhibit gene transcription, DNA replication, repair, or recombination. Acetylation has long been associated with chromatin opening and active gene transcription. Both individual nucleosomes and higher order chromatin folding can block access of RNA polymerase and other factors to gene promoters. Acetylation affects chromatin folding as the addition of the acetyl group neutralizes the positive charge of the lysine, weakening bonds between histones and the negatively charged DNA backbone, as well as the bonds between neighboring nucleosomes, allowing for more relaxed chromatin structures (Figure 1A). In addition, acetylation at specific lysine residues on particular histones can promote binding of regulatory factors involved in specific steps of the transcription process. For example, Histone H3 lysine 9 acetylation (H3K9ac), catalyzed largely by Gcn5/ PCAF, 4 is enriched at gene promoters, whereas H3K27ac, catalyzed largely by CBP/p300, is enriched at enhancer sequences. 5 These modifications promote binding of other factors through interactions with KAc reader domains, which are often located in other chromatin modifying proteins, including acetyltransferases, methyltransferases, and ATP-dependent chromatin remodelers such as Swi/Snf. 6C8 Open in a separate window Number 1 Mechanisms of action of acetylationA. KATs target both tails and globular domains of all 4 histone proteins. B. KATs acetylate non-histone proteins including transcription factors (TF) as well as metabolic enzymes and additional nuclear and cytoplasmic proteins. C. Bromodomain-containing proteins bind to acetyl-lysines on histone tails and on non-histone proteins. Readers of Acetyl-lysines: Bromodomains and YEATS domains Bromodomains were the 1st, and until recently, the only, acetyl-lysine binding domains explained. 9,10 These domains are highly conserved across development and many specifically bind acetylated lysines, while only poorly binding non-acetylated lysines, therefore reading the acetylation status of histones or additional proteins. 10 As such, bromodomains provide bridges for histone-protein and protein-protein relationships (Number 1C). The bromodomain family is split into many branches, each with different structural characteristics that provide specificity for different acetylation claims or proteins. 11 Although these family members possess wide variations in.