TRIM16 Acts as an E3 Ubiquitin Ligase and Can Heterodimerize with Other TRIM Family Members

Abstract

The TRIM family of proteins is distinguished by its tripartite motif (TRIM). Typically, TRIM proteins contain a RING finger domain, one or two B-box domains, a coiled-coil domain and the more variable C-terminal domains. TRIM16 does not have a RING domain but does harbour two B-box domains. Here we showed that TRIM16 homodimerized through its coiled-coil domain and heterodimerized with other TRIM family members; TRIM24, Promyelocytic leukaemia (PML) protein and Midline-1 (MID1). Although, TRIM16 has no classic RING domain, three-dimensional modelling of TRIM16 suggested that its B-box domains adopts RING-like folds leading to the hypothesis that TRIM16 acts as an ubiquitin ligase. Consistent with this hypothesis, we demonstrated that TRIM16, devoid of a classical RING domain had auto-polyubiquitination activity and acted as an E3 ubiquitin ligase in vivo and in vitro assays. Thus via its unique structure, TRIM16 possesses both heterodimerization function with other TRIM proteins and also has E3 ubiquitin ligase activity.

TRIMs and Galectins Globally Cooperate and TRIM16 and Galectin-3 Co-direct Autophagy in Endomembrane Damage Homeostasis

“…TRIM16 promoted ULK1 K63-linked ubiquitination (Figure 4F), a modification stabilizing autophagy regulators (Nazio et al, 2013). This action of TRIM16 could be either direct, since it has an E3 ubiquitin ligase activity (Bell et al, 2012) (confirmed in Figure S4A), or indirect by recruiting/activating other E3 ligases controlling activity of ULK1 (Nazio et al, 2013). The latter possibility was underscored by the co-immunoprecipitation of TRIM16 with cullin ubiquitin ligase components (Cullin 4A; Figure S4B) implicated in regulation of autophagy (Antonioli et al, 2014).…”

The MID1 E3 Ligase Catalyzes the Polyubiquitination of Alpha4 (α4), a Regulatory Subunit of Protein Phosphatase 2A (PP2A)

“…In our previous studies, the Bbox domains were shown to possess E3 ligase activity, albeit considerably less than the classic RING domain. On the other hand, the Bbox domains from TRIM16, which is technically not a TRIM protein because it lacks a RING domain but nevertheless has 28% identity to MID1 (40), were shown to facilitate polyubiquitination. We postulate that the binding of the C terminus of ␣4 to the Bbox1 domain alters the interface on Bbox1 that would typically be involved in E2-E3 interactions.…”

TRIM16 inhibits neuroblastoma cell proliferation through cell cycle regulation and dynamic nuclear localization

“…This LxxLL motif, which appears in many retinoid receptors, is required for tissue differentiation signaling 30 . Importantly, nuclear export/import of TRIM16 may involve specific NLS and NES sequence sites on TRIM16, binding to shuttling proteins and the homodimerization of TRIM16 or heterodimerization of TRIM16 to other TRIM proteins 14 . More research needs to be undertaken to fully explore the exact sequences and molecules involved in the actions of the coiled-coil and “linker” domain in the localization of the TRIM16 protein.…”

“…Many TRIM proteins, such as the tumor suppressor promeylocytic leukemia protein (PML/TRIM19), are highly expressed during G 1 phase and form PML bodies during G 1 and partition during mitosis 12 , 13 . Additionally, after retinoid treatment, TRIM16 protein co-localizes and homodimerizes with PML and forms nuclear bodies 4 , 14 . These nuclear bodies are also formed after cellular stress 15 - 17 .…”