This entry represents a group of E3 ubiquitin-protein ligases, including SP1 and SPL1 from Arabidopsis. They are E3 ubiquitin-protein ligases involved in the regulation of protein import in the chloroplast []. SP1 is associated with TOC (translocon at the outer envelope of chloroplasts) complexes and can mediate ubiquitination of TOC components, promoting their degradation [].This entry also includes some uncharacterised bacterial proteins.
This entry represents a short conserved region of activating transcription factor 7-interacting protein 1 found in higher eukaryotes. This domain appears to bind several key proteins such as TFIIE-alpha and TFIIE-beta as well the transcriptional regulator Sp1 which are part of the transcriptional machinery [].
This entry represents a group of putative E3 ubiquitin-protein ligases, including SPL2 from Arabidopsis. SPL2 shares topological similarity and considerable sequence identity with SP1, and is located in the chloroplast envelope []. SP1 is associated with TOC (translocon at the outer envelope of chloroplasts) complexes and mediates ubiquitination of TOC components, promoting their degradation [].
This entry represents engulfment and cell motility protein 3 (ELMO3) from vertebrates. The expression of ELMO3 may be regulated by transcription factors, such as CDX2 and SP1 []. ELMO3 has been linked to lung cancer development and metastases formation [].ELMO 1-3 are orthologues of the Caenorhabditis elegans ced-12, which is required for the engulfment of dying cells and cell migration []. They are cytoplasmic adaptor proteins that interact with DOCK family guanine nucleotide exchange factors (GEFs) to promote activation of the small GTPase Rac []. ELMO proteins interact with the SH3-domain of DOCKs via an SH3-binding site to enhance the GEF activity of DOCKs. Regulatory GTPases in the Ras superfamily employ a cycle of alternating GTP binding and hydrolysis, controlled by GEFs and GTPase-activating proteins (GAPs), as essential features of their actions in cells [, ].
This domain is found at the C terminus of Mesoderm induction early response proteins 1 and 3 (MIER1/3). MIER1 is a transcriptional repressor that regulates the expression of a number of genes including SP1 target genes, recruiting histone deacetylase 1 (HDAC1) through its ELM2 domain. It has two isoforms, alpha and beta, which differ in their C-terminal domains, both of them being able to interact with HDAC1. The gene encoding MIER3 has been identified as a candidate cancer susceptibility gene []. MIER1 and 3 share two regions of high homology, one at the N terminus and the second at the C terminus, represented in this entry, which consists of a short region located immediately downstream of the SANT extension that is 84% identical [, ].
This domain is found in mitochondrial ubiquitin ligase activator of NFKB 1 (MULAN, also known as MUL1) from animals and ubiquitin E3 Ligase SP1/SP2/SPL1/SPL2 from Arabidopsis.MUL1 is a multifunctional E3 ubiquitin ligase anchored in the outer mitochondrial membrane with its RING finger domain facing the cytoplasm. Mul1 functions as a ubiquitin ligase to ubiquitinate molecules such as mitofusin2 (Mfn2), Akt, p53 and ULK1, through its RING finger domain, leading to proteins degradation. Moreover, Mul1 can also act as a small ubiquitin-like modifiers (SUMO) E3 ligase to sumoylate proteins such as dynamin-related protein 1 (Drp1), enhancing protein stabilization []. It plays a role in the control of mitochondrial morphology, promotes mitochondrial fragmentation and influences mitochondrial localisation []. When over-expressed in human cells, it activates JNK through MAP3K7/TAK1 and induces caspase-dependent apoptosis []. MUL1 has also been shown to regulate RIG-I mediated antiviral response []. Ubiquitin E3 ligase SP1 associates with TOC (translocon at the outer envelope membrane of chloroplasts) complexes and mediates ubiquitination of TOC components, promoting their degradation. SP1-mediated regulation of chloroplast protein import contributes to the organellar proteome changes that occur during plant development []. It is also important for stress tolerance in plants [].
