Rabbit Anti-Human UBA1 (a.a. 91-140) Polyclonal antibody

Ubiquitination plays critical roles in the regulation of oncoproteins and tumor suppressors during carcinogenesis. The two ubiquitin activating enzymes (E1) in human genome, UBA1 and UBA6, initiate ubiquitination by ATP-dependent activation of ubiquitin. Recent evidence suggests that UBA1 and UBA6 play partially overlapped yet distinct roles in controlling the proteome. Here we demonstrate that ubiquitination pathways initiated specifically by UBA6 set a suppressive barrier against critical steps of mammary carcinogenesis such as loss of polarity, anoikis resistance and epithelial-mesenchymal transition (EMT). Mammary epithelial MCF-10A cells expressing shRNA against UBA6 fail in establishing cell cycle arrest in response to detachment from extracellular matrix, confluency with fully engaged cell-cell contact or growth factor deprivation. Moreover, UBA6-deficient MCF-10A cells undergo spontaneous EMT under growth factor deprivation and exhibit accelerated kinetics of TGF-beta-induced EMT. The Rho-GTPase CDC42 is one of the specific targets of UBA6-initiated ubiquitination and plays a key role in the function of UBA6 in controlling epithelial homeostasis, since a CDC42 inhibitor, ML141, rescues UBA6-deficient cells from the EMT phenotype. Immunohistochemical analysis of human breast cancer tissues demonstrates that 38% of invasive carcinomas express low or undetectable expression of UBA6, suggesting that downregulation of this non-canonical E1 plays a role in breast cancer development.

The activation of dendritic cells (DCs) is necessary to initiate immune responses. Angiotensin II (AngII) can enhance the maturation and activation of DCs, but the mechanisms are still unclear. Ubiquitin-activating enzyme (E1/Uba1) is the common first step in ubiquitylation, which decides whether or not the modified protein is ultimately degraded by the proteasome. This study aimed to investigate the role of E1 in AngII-induced activation of DCs and the underlying mechanisms. First, we showed that AngII stimulation significantly up-regulated E1 expression in DCs. Moreover, AngII treatment markedly induced phenotypic maturation, the secretion of cytokines and the immunostimulatory capacity of DCs. In contrast, inhibition of E1 by a small molecule inhibitor, 4[4-(5-nitro-furan-2-ylmethylene)-3, 5-dioxo-pyrazolidin-1-yl]-benzoic acid ethyl ester (PYR41), markedly attenuated these effects. Mechanistically, PYR41 treatment markedly decreased K63-linked ubiquitination of tumour necrosis factor receptor-associated factor 6 and nuclear factor-B essential modulator, inhibited proteasomal degradation of nuclear factor-B inhibitor and mitogen-activated protein kinase phosphatase 1 thereby resulting in activation of nuclear factor-B, extracellular signal-regulated kinase 1/2 and signal transducer and activator of transcription 1 signalling pathways in DCs induced by AngII. Taken together, our results demonstrate a novel role of E1 in AngII-induced activation of DCs, and inhibition of E1 activity might be a potential therapeutic target for DC-mediated autoimmune diseases.