The melanoma-associated antigen 1 (MAGEA1) protein stimulates the E3 ubiquitin-ligase activity of TRIM31 within a TRIM31-MAGEA1-NSE4 complex

The MAGE (Melanoma-associated antigen) protein family members are structurally related to each other by a MAGE-homology domain comprised of 2 winged helix motifs WH/A and WH/B. This family specifically evolved in placental mammals although single homologs designated NSE3 (non-SMC element) exist in most eukaryotes. NSE3, together with its partner proteins NSE1 and NSE4 form a tight subcomplex of the structural maintenance of chromosomes SMC5–6 complex. Previously, we showed that interactions of the WH/B motif of the MAGE proteins with their NSE4/EID partners are evolutionarily conserved (including the MAGEA1-NSE4 interaction). In contrast, the interaction of the WH/A motif of NSE3 with NSE1 diverged in the MAGE paralogs. We hypothesized that the MAGE paralogs acquired new RING-finger-containing partners through their evolution and form MAGE complexes reminiscent of NSE1-NSE3-NSE4 trimers. In this work, we employed the yeast 2-hybrid system to screen a human RING-finger protein library against several MAGE baits. We identified a number of potential MAGE-RING interactions and confirmed several of them (MDM4, PCGF6, RNF166, TRAF6, TRIM8, TRIM31, TRIM41) in co-immunoprecipitation experiments. Among these MAGE-RING pairs, we chose to examine MAGEA1-TRIM31 in detail and showed that both WH/A and WH/B motifs of MAGEA1 bind to the coiled-coil domain of TRIM31 and that MAGEA1 interaction stimulates TRIM31 ubiquitin-ligase activity. In addition, TRIM31 directly binds to NSE4, suggesting the existence of a TRIM31-MAGEA1-NSE4 complex reminiscent of the NSE1-NSE3-NSE4 trimer. These results suggest that MAGEA1 functions as a co-factor of TRIM31 ubiquitin-ligase and that the TRIM31-MAGEA1-NSE4 complex may have evolved from an ancestral NSE1-NSE3-NSE4 complex.

Trim27-deficient mice are susceptible to streptozotocin-induced diabetes

Tumor necrosis factor α (TNF-α) plays an important role in cell proliferation and apoptosis, and defects in TNF-α-induced apoptosis are associated with various diseases. TRIM27 is a tripartite motif (TRIM) protein containing RING finger, B-box, and coiled-coil domains. We recently reported that TRIM27 positively regulates TNF-α-induced apoptosis through deubiquitination of receptor-interacting protein 1 (RIP1). Multiple studies have suggested a link between TNF-α pathway and various diseases, such as diabetes and colitis. Here, we report that Trim27-deficient mice were susceptible to streptozotocin (STZ)-induced diabetes, a mouse model of diabetes. Infiltration of T cells and cleaved caspase-3 signals were enhanced, and β-cell mass was decreased in Trim27-deficient islets compared to wild-type islets. On the other hand, Trim27-mutation did not affect the dextran sodium sulphate (DSS)-induced colitis. These data support the idea that the TRIM27 mutation is responsible for the development of certain types of diseases.

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Trim27-deficient mice are susceptible to streptozotocin-induced diabetes.

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Infiltration of T cells is enhanced in Trim27-deficient islets.

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Beta-cell mass was decreased in Trim27-deficient islets.

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Trim27-deficient mice are not susceptible to dextran sodium sulphate-induced colitis.