TRRAP

TRRAP
National Center for Biotechnology Information, U.S. National Library of Medicine · Public domain · source
Name	Transformation/transcription domain-associated protein
Alt	TRAAP
Uniprot	Q9Y4X5
Organism	Homo sapiens

TRRAP

Transformation/transcription domain-associated protein (commonly known by the symbol TRRAP) is a large human nuclear protein that functions as a scaffold in multiple chromatin-modifying complexes involved in transcriptional activation, DNA damage response, and cell-cycle control. It bridges interactions between transcription factors and histone acetyltransferase assemblies, coordinating activities that include chromatin remodeling, histone acetylation, and signaling cascades implicated in development and oncogenesis. TRRAP is conserved across eukaryotes and has been studied in diverse model systems and clinical contexts.

Function and Mechanism

TRRAP acts primarily as a non-catalytic scaffolding subunit that recruits histone acetyltransferase complexes to promoters and enhancers targeted by transcription factors such as c-Myc, E2F1, p53, NF-κB, and ATF2. Through interactions with chromatin modifiers including GCN5, PCAF, and the Tip60 complex, TRRAP facilitates acetylation of histones H3 and H4, promoting transcriptional activation at loci controlled by regulators like Myc target genes, HOXA9-regulated elements, and Notch-responsive promoters. TRRAP participates in the DNA damage response by enabling recruitment of ATM-dependent signaling components and chromatin remodelers to sites of double-strand breaks, coordinating repair pathways that overlap with factors such as BRCA1, MDC1, and RAD51. Mechanistically, TRRAP influences nucleosome dynamics and enhancer accessibility, linking sequence-specific transcription factors to general chromatin-modifying activities seen in pathways involving Wnt/β-catenin, Hedgehog, and TP53-regulated networks.

Structure and Biochemistry

TRRAP is an approximately 434 kDa protein composed of multiple conserved domains that mediate protein–protein interactions, including HEAT repeat-like motifs and regions homologous to phosphatidylinositol 3-kinase-related kinases (PIKK) but lacking catalytic kinase activity. Structural studies using cryo-electron microscopy and crosslinking mass spectrometry have mapped contact surfaces between TRRAP and subunits of the SAGA-like and TIP60 complexes, revealing interfaces with GCN5, ADA2B, ING3, and EP400. Post-translational modifications of TRRAP include phosphorylation by kinases such as ATM and ATR and acetylation events that modulate its affinity for transcriptional regulators like c-Myc and E2F1. Biochemically, TRRAP-containing assemblies display histone acetyltransferase activity through associated enzymes, and in vitro reconstitution assays show TRRAP-dependent stimulation of nucleosome acetylation and remodeling activities akin to those mediated by SWI/SNF and NuRD cofactors.

Genetics and Regulation

The human TRRAP gene resides on chromosome 7 and is subject to transcriptional and post-transcriptional regulation involving promoter elements and RNA-binding factors that intersect with signaling pathways mediated by PI3K, MAPK, and TGF-β. Genetic screens in yeast and Drosophila identified orthologs that are essential for viability and for regulation of developmental transcriptional programs directed by factors such as GAL4 and dMyc. Somatic alterations affecting the TRRAP locus, including mutations and copy-number changes, have been reported in tumor sequencing efforts involving cohorts curated by The Cancer Genome Atlas and clinical studies of neuroblastoma, glioma, and leukemia. Transcriptional regulation of TRRAP itself can be influenced by transcription factors such as SP1, MYC, and hormone receptors including AR and ERα, linking TRRAP expression to proliferative and differentiation cues.

Role in Development and Disease

TRRAP is required for embryonic development and tissue homeostasis, with loss-of-function alleles producing embryonic lethality in mouse models and developmental defects in zebrafish and Drosophila. In the context of disease, TRRAP contributes to oncogenic programs by cooperating with oncoproteins like c-Myc and E2F3 to promote proliferation, and TRRAP-associated complexes regulate genes implicated in cell cycle progression and apoptosis mediated by p53. Mutations in TRRAP and dysregulation of TRRAP-containing complexes have been implicated in cancers such as medulloblastoma, breast cancer, and pancreatic adenocarcinoma, and alterations may affect sensitivity to chemotherapeutic agents and radiotherapy via impaired DNA damage signaling involving ATM and CHK2. Beyond cancer, TRRAP dysfunction has been tied to neurodevelopmental disorders and neurodegeneration through impacts on chromatin states that regulate neuronal differentiation programs governed by transcription factors including REST, NeuroD1, and SOX2.

Interactions and Complexes

TRRAP is a core component of multiple multiprotein assemblies, notably the human SAGA-like complex and the TIP60 histone acetyltransferase complex, interacting with subunits such as GCN5, ADA2A/B, TRIM33, EP400, DMAP1, ING3, and KAT5. It associates with sequence-specific factors including c-Myc, E2F1, p53, NF-κB, STAT3, and HIF1A, facilitating recruitment of acetyltransferases and chromatin remodelers to responsive promoters and enhancers. Proteomic surveys using affinity purification–mass spectrometry have revealed dynamic interaction networks linking TRRAP to chromatin remodelers such as INO80 and SWR1 components, as well as to ubiquitin ligases and histone deubiquitinases involved in transcriptional control and DNA repair processes regulated by RNF20 and BRCA1.

Experimental Studies and Models

Functional interrogation of TRRAP has employed conditional knockout mice, RNA interference, CRISPR/Cas9-mediated gene editing, and protein complementation assays in human cell lines including HeLa, HEK293, and U2OS. Studies using chromatin immunoprecipitation followed by sequencing in models such as mouse embryonic stem cells and human cancer cell lines have mapped TRRAP occupancy at promoters for genes regulated by Myc, E2F, and p53. Chemical biology approaches using acetyltransferase inhibitors and synthetic lethality screens in libraries curated by consortia like Cancer Dependency Map have probed TRRAP-dependent vulnerabilities in tumor cells. Developmental roles have been elucidated in Drosophila melanogaster models and murine embryogenesis, where TRRAP perturbation alters morphogenetic programs driven by Notch, Wnt, and BMP signaling.

Category:Human proteins