Histone acetyltransferase p300 also known as p300 HAT or E1A-associated protein p300 (where E1A = adenovirus early region 1A) also known as EP300 or p300 is an enzyme that, in humans, is encoded by the EP300 gene. [5] It functions as histone acetyltransferase that regulates transcription of genes via chromatin remodeling by allowing histone proteins to wrap DNA less tightly. This enzyme plays an essential role in regulating cell growth and division, prompting cells to mature and assume specialized functions (differentiate), and preventing the growth of cancerous tumors. The p300 protein appears to be critical for normal development before and after birth.
The EP300 gene is located on the long (q) arm of the human chromosome 22 at position 13.2. This gene encodes the adenovirus E1A-associated cellular p300 transcriptional co-activator protein.
EP300 is closely related to another gene, CREB binding protein, which is found on human chromosome 16.
p300 HAT functions as histone acetyltransferase [6] that regulates transcription via chromatin remodeling, and is important in the processes of cell proliferation and differentiation. It mediates cAMP-gene regulation by binding specifically to phosphorylated CREB protein.
p300 HAT contains a bromodomain which is involved in IL6 signaling. [7] : 3.1
This gene has also been identified as a co-activator of HIF1A (hypoxia-inducible factor 1 alpha), and, thus, plays a role in the stimulation of hypoxia-induced genes such as VEGF. [8]
The p300 protein carries out its function of activating transcription by binding to transcription factors, and the transcription machinery. On the basis of this function, p300 is called a transcriptional coactivator. The p300 interaction with transcription factors is managed by one or more of p300 domains: the nuclear receptor interaction domain (RID), the KIX domain (CREB and MYB interaction domain), the cysteine/histidine regions (TAZ1/CH1 and TAZ2/CH3) and the interferon response binding domain (IBiD). The last four domains, KIX, TAZ1, TAZ2 and IBiD of p300, each bind tightly to a sequence spanning both transactivation domains 9aaTADs of transcription factor p53. [9]
Mutations in the EP300 gene are responsible for a small percentage of cases of Rubinstein-Taybi syndrome. These mutations result in the loss of one copy of the gene in each cell, which reduces the amount of p300 protein by half. Some mutations lead to the production of a very short, nonfunctional version of the p300 protein, while others prevent one copy of the gene from making any protein at all. Although researchers do not know how a reduction in the amount of p300 protein leads to the specific features of Rubinstein-Taybi syndrome, it is clear that the loss of one copy of the EP300 gene disrupts normal development.[ citation needed ]
Chromosomal rearrangements involving chromosome 22 have rarely been associated with certain types of cancer. These rearrangements, called translocations, disrupt the region of chromosome 22 that contains the EP300 gene. For example, researchers have found a translocation between chromosomes 8 and 22 in several people with a cancer of blood cells called acute myeloid leukemia (AML). Another translocation, involving chromosomes 11 and 22, has been found in a small number of people who have undergone cancer treatment. This chromosomal change is associated with the development of AML following chemotherapy for other forms of cancer.[ citation needed ]
Mutations in the EP300 gene have been identified in several other types of cancer. These mutations are somatic, which means they are acquired during a person's lifetime and are present only in certain cells. Somatic mutations in the EP300 gene have been found in a small number of solid tumors, including cancers of the colon and rectum, stomach, breast, and pancreas. Studies suggest that EP300 mutations may also play a role in the development of some prostate cancers, and could help predict whether these tumors will increase in size or spread to other parts of the body. In cancer cells, EP300 mutations prevent the gene from producing any functional protein. Without p300, cells cannot effectively restrain growth and division, which can allow cancerous tumors to form.[ citation needed ]
EP300 has been shown to interact with:
The p300-CBP coactivator family in humans is composed of two closely related transcriptional co-activating proteins :
P300/CBP-associated factor (PCAF), also known as K(lysine) acetyltransferase 2B (KAT2B), is a human gene and transcriptional coactivator associated with p53.
CREB-binding protein, also known as CREBBP or CBP or KAT3A, is a coactivator encoded by the CREBBP gene in humans, located on chromosome 16p13.3. CBP has intrinsic acetyltransferase functions; it is able to add acetyl groups to both transcription factors as well as histone lysines, the latter of which has been shown to alter chromatin structure making genes more accessible for transcription. This relatively unique acetyltransferase activity is also seen in another transcription enzyme, EP300 (p300). Together, they are known as the p300-CBP coactivator family and are known to associate with more than 16,000 genes in humans; however, while these proteins share many structural features, emerging evidence suggests that these two co-activators may promote transcription of genes with different biological functions.
Interferon regulatory factor 3, also known as IRF3, is an interferon regulatory factor.
The nuclear receptor coactivator 2 also known as NCoA-2 is a protein that in humans is encoded by the NCOA2 gene. NCoA-2 is also frequently called glucocorticoid receptor-interacting protein 1 (GRIP1), steroid receptor coactivator-2 (SRC-2), or transcriptional mediators/intermediary factor 2 (TIF2).
The nuclear receptor coactivator 3 also known as NCOA3 is a protein that, in humans, is encoded by the NCOA3 gene. NCOA3 is also frequently called 'amplified in breast 1' (AIB1), steroid receptor coactivator-3 (SRC-3), or thyroid hormone receptor activator molecule 1 (TRAM-1).
Retinoid X receptor alpha (RXR-alpha), also known as NR2B1 is a nuclear receptor that in humans is encoded by the RXRA gene.
Histone acetyltransferase KAT2A is an enzyme that in humans is encoded by the KAT2A gene.
C-terminal-binding protein 1 also known as CtBP1 is a protein that in humans is encoded by the CTBP1 gene. CtBP1 is one of two CtBP proteins, the other protein being CtBP2.
Myocyte-specific enhancer factor 2A is a protein that in humans is encoded by the MEF2A gene. MEF2A is a transcription factor in the Mef2 family. In humans it is located on chromosome 15q26. Certain mutations in MEF2A cause an autosomal dominant form of coronary artery disease and myocardial infarction.
Cux1 is a homeodomain protein that in humans is encoded by the CUX1 gene.
TAF9 RNA polymerase II, TATA box binding protein (TBP)-associated factor, 32kDa, also known as TAF9, is a protein that in humans is encoded by the TAF9 gene.
Transcription initiation factor TFIID subunit 4 is a protein that in humans is encoded by the TAF4 gene.
Nuclear receptor coactivator 6 is a protein that in humans is encoded by the NCOA6 gene.
Cbp/p300-interacting transactivator 2 is a protein that in humans is encoded by the CITED2 gene.
Cbp/p300-interacting transactivator 1 is a protein that in humans is encoded by the CITED1 gene.
TAF5-like RNA polymerase II p300/CBP-associated factor-associated factor 65 kDa subunit 5L is an enzyme that in humans is encoded by the TAF5L gene.
In molecular biology, TAZ zinc finger domains are zinc-containing domains found in the homologous transcriptional co-activators CREB-binding protein (CBP) and the P300. CBP and P300 are histone acetyltransferases that catalyse the reversible acetylation of all four histones in nucleosomes, acting to regulate transcription via chromatin remodelling. These large nuclear proteins interact with numerous transcription factors and viral oncoproteins, including p53 tumour suppressor protein, E1A oncoprotein, MyoD, and GATA-1, and are involved in cell growth, differentiation and apoptosis. Both CBP and P300 have two copies of the TAZ domain, one in the N-terminal region, the other in the C-terminal region. The TAZ1 domain of CBP and P300 forms a complex with CITED2, inhibiting the activity of the hypoxia inducible factor (HIF-1alpha) and thereby attenuating the cellular response to low tissue oxygen concentration. Adaptation to hypoxia is mediated by transactivation of hypoxia-responsive genes by hypoxia-inducible factor-1 (HIF-1) in complex with the CBP and p300 transcriptional coactivators.
In biochemistry, the KIX domain (kinase-inducible domain (KID) interacting domain) or CREB binding domain is a protein domain of the eukaryotic transcriptional coactivators CBP and P300. It serves as a docking site for the formation of heterodimers between the coactivator and specific transcription factors. Structurally, the KIX domain is a globular domain consisting of three α-helices and two short 310-helices.
The transactivation domain or trans-activating domain (TAD) is a transcription factor scaffold domain which contains binding sites for other proteins such as transcription coregulators. These binding sites are frequently referred to as activation functions (AFs). TADs are named after their amino acid composition. These amino acids are either essential for the activity or simply the most abundant in the TAD. Transactivation by the Gal4 transcription factor is mediated by acidic amino acids, whereas hydrophobic residues in Gcn4 play a similar role. Hence, the TADs in Gal4 and Gcn4 are referred to as acidic or hydrophobic, respectively.
This article incorporates text from the United States National Library of Medicine, which is in the public domain.