This entry represents the RNA recognition motif 1 (RRM1) of SART3 (also known as Tip110), which is an RNA-binding protein expressed in the nucleus of the majority of proliferating cells, including normal cells and malignant cells, but not in normal tissues except for the testes and fetal liver []. It is involved in the regulation of mRNA splicing probably via its complex formation with RNPS1 (an RNA-binding protein with a serine-rich domain), a pre-mRNA-splicing factor []. SART3 has also been identified as a nuclear Tat-interacting protein that regulates Tat transactivation activity through direct interaction and functions as an important cellular factor for HIV-1 gene expression and viral replication []. In addition, SART3 is required for U6 snRNP targeting to Cajal bodies []. It binds specifically and directly to the U6 snRNA, interacts transiently with the U6 and U4/U6 snRNPs, and promotes the reassembly of U4/U6 snRNPs after splicing in vitro [].SART3 contains an N-terminal HAT (half-a-tetratricopeptide repeat)-rich domain, a nuclearlocalization signal (NLS) domain, and two C-terminal RNA recognition motifs (RRMs).
This entry represents the RNA recognition motif 2 (RRM2) of SART3 (also known as Tip110), which is an RNA-binding protein expressed in the nucleus of the majority of proliferating cells, including normal cells and malignant cells, but not in normal tissues except for the testes and fetal liver []. It is involved in the regulation of mRNA splicing probably via its complex formation with RNPS1 (an RNA-binding protein with a serine-rich domain), a pre-mRNA-splicing factor []. SART3 has also been identified as a nuclear Tat-interacting protein that regulates Tat transactivation activity through direct interaction and functions as an important cellular factor for HIV-1 gene expression and viral replication []. In addition, SART3 is required for U6 snRNP targeting to Cajal bodies []. It binds specifically and directly to the U6 snRNA, interacts transiently with the U6 and U4/U6 snRNPs, and promotes the reassembly of U4/U6 snRNPs after splicing in vitro [].SART3 contains a HAT (N-terminal half-a-tetratricopeptide repeat)-rich domain, a nuclearlocalization signal (NLS) domain, and two C-terminal RNA recognition motifs (RRMs).
This entry represent the C3HC5-type RING-HC finger found in MGRN1/RNF157 and related proteins. It is distinguished from typical C3HC4 RING-HC finger due to the existence of the additional cysteine residue in the middle portion of the RING finger domain.MGRN1 is a cytosolic E3 ubiquitin-protein ligase that inhibits signalling through the G protein-coupled melanocortin receptors-1 (MC1R), -2 (MC2R) and -4 (MC4R) via ubiquitylation-dependent and -independent processes []. It suppresses chaperone-associated misfolded protein aggregation and toxicity []. MGRN1 interacts with cytosolic prion proteins (PrPs) that are linked with neurodegeneration[]. It also interacts with expanded polyglutamine proteins, and suppresses misfolded polyglutamine aggregation and cytotoxicity. Moreover, MGRN1 inhibits melanocortin receptor signaling by competition with Galphas, suggesting a novel pathway for melanocortin signaling from the cell surface to the nucleus []. Furthermore, MGRN1 interacts with and ubiquitylates TSG101, a key component of the endosomal sorting complex required for transport (ESCRT)-I, and regulates endosomal trafficking. A null mutation in the gene encoding MGRN1 causes spongiform neurodegeneration, suggesting a link between dysregulation of endosomal trafficking and spongiform neurodegeneration [, ].RNF157 is a cytoplasmic E3 ubiquitin ligase predominantly expressed in brain. In cultured neurons, it promotes neuronal survival in an E3 ligase-dependent manner. In contrast, it supports growth and maintenance of dendrites independent of its E3 ligase activity. RNF157 interacts with and ubiquitinates the adaptor protein APBB1 (amyloid beta precursor protein-binding, family B, member 1 or Fe65), which regulates neuronal survival, but not dendritic growth downstream of RNF157. The nuclear localization of APBB1 together with its interaction partner RNA-binding protein SART3 (squamous cell carcinoma antigen recognized by T cells 3 or Tip110) is crucial to trigger apoptosis []. Both MGRN1 and RNF157 contain a modified C3HC5-type RING-HC finger, and a functionally uncharacterized region, known as domain associated with RING2 (DAR2), N-terminal to the RING finger.In Arabidopsis, LOG2 is a predicted E3 ubiquitin ligase that interact with GDU1 and is involved in the regulation of amino acid export from plant cells [].
This entry represents a group of confirmed and predicted E3 ubiquitin ligases, including MGRN1/RNF157 from humans and LOG2/LUL1-4 from Arabidopsis.MGRN1 is a cytosolic E3 ubiquitin-protein ligase that inhibits signalling through the G protein-coupled melanocortin receptors-1 (MC1R), -2 (MC2R) and -4 (MC4R) via ubiquitylation-dependent and -independent processes []. It suppresses chaperone-associated misfolded protein aggregation and toxicity []. MGRN1 interacts with cytosolic prion proteins (PrPs) that are linked with neurodegeneration[]. It also interacts with expanded polyglutamine proteins, and suppresses misfolded polyglutamine aggregation and cytotoxicity. Moreover, MGRN1 inhibits melanocortin receptor signaling by competition with Galphas, suggesting a novel pathway for melanocortin signaling from the cell surface to the nucleus []. Furthermore, MGRN1 interacts with and ubiquitylates TSG101, a key component of the endosomal sorting complex required for transport (ESCRT)-I, and regulates endosomal trafficking. A null mutation in the gene encoding MGRN1 causes spongiform neurodegeneration, suggesting a link between dysregulation of endosomal trafficking and spongiform neurodegeneration [, ].RNF157 is a cytoplasmic E3 ubiquitin ligase predominantly expressed in brain. In cultured neurons, it promotes neuronal survival in an E3 ligase-dependent manner. In contrast, it supports growth and maintenance of dendrites independent of its E3 ligase activity. RNF157 interacts with and ubiquitinates the adaptor protein APBB1 (amyloid beta precursor protein-binding, family B, member 1 or Fe65), which regulates neuronal survival, but not dendritic growth downstream of RNF157. The nuclear localization of APBB1 together with its interaction partner RNA-binding protein SART3 (squamous cell carcinoma antigen recognized by T cells 3 or Tip110) is crucial to trigger apoptosis []. Both MGRN1 and RNF157 contain a modified C3HC5-type RING-HC finger, and a functionally uncharacterized region, known as domain associated with RING2 (DAR2), N-terminal to the RING finger.In Arabidopsis, LOG2 is a predicted E3 ubiquitin ligase that interact with GDU1 and is involved in the regulation of amino acid export from plant cells [].
