E3 ubiquitin-protein ligase Topors; SUMO1-protein E3 ligase Topors; Topoisomerase I-binding RING finger protein; Topoisomerase I-binding arginine/serine-rich protein; tumor suppressor p53-binding protein 3; p53-binding protein 3; p53BP3 (TOPORS, LUN, TP53BPL)
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Function
- ubiquitin-protein E3 ligase
- E3 SUMO1-protein ligase
- ubiquitinates & sumoylates p53
- regulates p53/TP53 stability through ubiquitin-dependent degradation.
- probable tumor suppressor involved in cell growth, cell proliferation & apoptosis
- may regulate chromatin modification through sumoylation of several chromatin modification-associated proteins
- may be involved in DNA damage-induced cell death through IKBKE sumoylation
- phosphorylation at Ser-98
- regulates E3 ubiquitin-protein ligase activity
- does not regulate SUMO1-protein ligase activity
- phosphorylation at Ser-718
- increases E3 ubiquitin-protein ligase activity versus the SUMO1-protein ligase activity
- results in increased p53/TP53 ubiquitination & degradation
- polyubiquitinates NKX3-1 & induces its proteasomal degradation
- sumoylates SIN3A
- interacts with PARK7, TOP1, p53, UBE2I, NKX3-1, SIN3A, IKBKE, SUMO1
- sumoylated
Structure
contains 1 RING-type Zn+2 finger
Compartment
- nucleus
- localizes to discrete nuclear foci, partly overlap with PML nuclear bodies
Alternative splicing
named isoforms=2
Expression
- expressed in testis > adrenal gland, bone marrow, brain, colon, heart, kidney, liver, muscle, ovary, pancreas, placenta, prostate, skeletal muscle, skin, small intestine, spleen, stomach, testis, thymus, thyroid, uterus, alveolar epithelium of the lung
- induction by genotoxic agents such as cisplatin & camptothecin
Pathology
- defects in TOPORS are the cause of retinitis pigmentosa type 31
- expression is commonly decreased in: