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ARID/BRIGHT DNA binding domain of AT-rich interactive domain-containing protein 3A (ARID3A) and similar proteins ARID3A, also called B-cell regulator of IgH transcription (Bright), dead ringer-like protein 1 (Dril1), or E2F-binding protein 1 (E2FBP1), is an ubiquitously expressed DNA-binding protein that has been implicated in embryonic patterning, cell lineage gene regulation, and cell cycle control, chromatin remodeling and transcriptional regulation. It was originally identified as a B cell-specific trans-activator of immunoglobulin heavy-chain (IgH) transcription, which increases immunoglobulin transcription in antigen-activated B cells and plays regulatory roles in hematopoiesis. It also functions as an E2F transcription regulator, inducing promyelocytic leukemia protein (PML) reduction and suppressing the formation of PML-nuclear bodies. It antagonizes the p16(INK4A)-Rb tumor suppressor machinery by regulating PML stability. ARID3A transcriptional activity can be modulated by SUMO (Small Ubiquitin-related Modifier) modification through the interaction with the SUMO-conjugating enzyme Ubc9. ARID3A also plays an important role in marginal zone B lymphocyte development and autoantibody production. Furthermore, ARID3A is a direct p53 target gene. It controls cell growth in a p53-dependent manner. ARID3A contains an AT-rich DNA-interacting domain (ARID, also known as BRIGHT), a SUMO-I conjugation (SUMO) motif and a multifunctional homomerization/nuclear export REKLES domain, which consists of two subdomains: a modestly conserved N-terminal REKLES alpha and a highly conserved (among ARID3 orthologous proteins) C-terminal REKLES beta.
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