Deltex E3 ubiquitin ligase 3L is a protein that in humans is encoded by the DTX3L gene. [5] It functions as an ubiquitin ligase (E3), [6] and is over-expressed in chemotherapy-resistant lymphomas. [7] It is a member of the DTX family of proteins. [8] Among other roles it has a function in DNA damage repair.
It was discovered through two-hybrid screening during a search for binding partners of PARP9 (formerly BAL [9] ), a gene related to the risk of B-cell lymphoma. and was originally named BBAP (B-lymphoma- and BAL-associated protein). [6]
DTX3L and PARP9 are both located in the same 48kB region of the genome, and are both regulated by a IFN-γ-responsive bidirectional promoter. [10] DTX3L has a long N-terminus domain distinct from other DTX-family proteins that allows it form dimers with itself and other proteins. [8] It has been found to be up-regulated by METTL3. [8]
DTX3L functions as an ubiquitin ligase or E3. [6] These proteins bind to ubiquitin-conjugating enzymes (E2s), and then transfer and bind the ubiquitin (activated by E1s) from the E2s to the target protein. [11] Along with all other known DTX-family proteins (as of 2023), DTX3L is involved in the regulation of Notch signaling. [8]
DTX3L also plays a role in DNA damage repair, [8] which has been associated with its ability to selectively mono-ubiquitylate (bind one ubiquitin to) histone H4. [7] [8] It helps to protect cells exposed to DNA damaging agents. [7]
DTX3L can form a complex with PARP9. [12] This complex functions as a ubiquitin ligase and ubiquitinates both host histone H2BJ, to promote expression of interferon-stimulated genes, and viral 3C protease to disrupt viral assembly. [12] This can help to control viral infection. [12] PARP9 can also affect DXT3L's function in DNA damage repair. [8] The DXT3L-PARP9 complex mediates mono-ADP-ribosylation of ubiquitin; this prevents it from being conjugated [13] and inhibits DXT3L's function as an ubiquitin ligase. [8] The NAD+ dependent binding of PARP9 to poly-ADP-ribose, instead, enhances the activity of DXT3L as a ubiquitin ligase. [8] [ why? ] DTX3L can also form a complex with DTX1. [8]
DTX3L also affects signaling by inhibiting the sorting of the G-protein coupled receptor CXCR4 through the endosomes to degradation in the lysosomes. [14] When CXCR4 is activated, DXT3L localizes to early endosomes and inhibits the E3 ubiquitin ligase atrophin-1 interacting protein 4. [14] This reduces the extent to which the protein ESCRT-0 is ubiquitinated, which reduces its ability to sort CXCR4 into the lysosomes. [14] The implications of this effect (as of 2023) in cancer biology are unknown. [8]
ITCH is a HECT domain–containing E3 ubiquitin ligase that is ablated in non-agouti-lethal 18H mice. Itchy mice develop a severe immunological phenotype after birth that includes hyperplasia of lymphoid and hematopoietic cells, and stomach and lung inflammation. In humans ITCH deficiency causes altered physical growth, craniofacial morphology defects, defective muscle development, and aberrant immune system function. The ITCH gene is located on chromosome 20 in humans. ITCH contains a C2 domain, proline-rich region, WW domains, HECT domain, and multiple amino acids that are phosphorylated and ubiquitinated.
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This article incorporates text from the United States National Library of Medicine, which is in the public domain.