RING finger (Really Interesting New Gene) domain and U-box domain superfamily; The RING finger is a specialized type of Zn-finger of 40 to 60 residues that binds two atoms of zinc. It is defined by the "cross-brace" motif that chelates zinc atoms by eight amino acid residues, typically Cys or His, arranged in a characteristic spacing. Canonical RING motifs have been categorized into two major subclasses, RING-HC (C3HC4-type) and RING-H2 (C3H2C3-type), according to their Cys/His content. There are also many variants of RING fingers: some have different Cys/His patterns while some lack a single Cys or His residue at typical Zn ligand positions (the fourth or eighth zinc ligand is prevalently exchanged for an Asp, which can indeed chelate Zn in a RING finger as well). C4C4-, C3HC3D-, C2H2C4-, and C3HC5-type RING fingers are closely related to RING-HC fingers. In contrast, C4HC3- (RING-CH alias RINGv), C3H3C2-, C3H2C2D-, C3DHC3-, and C4HC2H-type RING fingers are more closely related to RING-H2 fingers. However, not all RING finger-containing proteins display regular RING finger features, and the RING finger family has turned out to be multifarious. The degenerate RING fingers of the Siz/PIAS RING (SP-RING) family proteins and sporulation protein RMD5, are characterized by lacking the second, fifth, and sixth Zn2+ ion-coordinating residues. They bind only one Zn2+ ion. On the other hand, the RING fingers of the human APC11 and RBX1 proteins can bind a third Zn atom since they harbor four additional Zn ligands. U-box is a modified form of the RING finger domain that lacks metal chelating Cys and His residues. It resembles the cross-brace RING structure consisting of three beta-sheets and a single alpha-helix, which would be stabilized by salt bridges instead of chelated metal ions. U-box proteins are widely distributed among eukaryotic organisms and show a higher prevalence in plants than in other organisms. RING finger/U-box-containing proteins are a group of diverse proteins with a variety of cellular functions, including oncogenesis, development, viral replication, signal transduction, the cell cycle and apoptosis. Many of them are ubiquitin-protein ligases (E3s) that serve as scaffolds for binding to ubiquitin-conjugating enzymes (E2s, also referred to as ubiquitin carrier proteins or UBCs) in close proximity to substrate proteins, which enable efficient transfer of ubiquitin from E2 to the substrates.

                        10        20        30        40
                ....*....|....*....|....*....|....*....|....
gi 30794158 196 KQCVACQERAHGTVLRPCQHRVLCEPCAASTPECPYCKGQPLPW 239
Cdd:cd16772   1 KKCIVCQERDRSIVLQPCQHYVLCEHCAASKPECPYCKTKILKW 44

RING finger, HC subclass, found in RING finger protein unkempt-like (UNKL) and similar proteins; UNKL, also known as zinc finger CCCH domain-containing protein 5-like, is a putative E3 ubiquitin-protein ligase that may participate in a protein complex showing an E3 ligase activity regulated by RAC1. It shows high sequence similarity with RING finger protein unkempt (UNK), which is a metazoan-specific zinc finger protein enriched in embryonic brains, and may play a broad regulatory role during the formation of the central nervous system (CNS). UNKL contains several CCCH-type zinc fingers at the N-terminus, and a C3HC4-type RING-HC finger at its C-terminus.

                        10        20        30        40
                ....*....|....*....|....*....|....*....|....
gi 30794158 196 KQCVACQERAHGTVLRPCQHRVLCEPCAASTPECPYCKGQPLPW 239
Cdd:cd16772   1 KKCIVCQERDRSIVLQPCQHYVLCEHCAASKPECPYCKTKILKW 44

Uncharacterized conserved protein, contains a C-terminal ATPase domain [Function unknown];

                         10        20        30        40        50        60        70
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....
gi 30794158   76 ELARVRRQLDEAKRKIRQWEESWQQVKQACDAWQREAQEAKERARVADSD-RQLALQRKEEVEAKVKQLQEELE 148
Cdd:COG4913  282 RLWFAQRRLELLEAELEELRAELARLEAELERLEARLDALREELDELEAQiRGNGGDRLEQLEREIERLERELE 355

RING finger, HC subclass, found in RING finger protein unkempt-like (UNKL) and similar proteins; UNKL, also known as zinc finger CCCH domain-containing protein 5-like, is a putative E3 ubiquitin-protein ligase that may participate in a protein complex showing an E3 ligase activity regulated by RAC1. It shows high sequence similarity with RING finger protein unkempt (UNK), which is a metazoan-specific zinc finger protein enriched in embryonic brains, and may play a broad regulatory role during the formation of the central nervous system (CNS). UNKL contains several CCCH-type zinc fingers at the N-terminus, and a C3HC4-type RING-HC finger at its C-terminus.

                        10        20        30        40
                ....*....|....*....|....*....|....*....|....
gi 30794158 196 KQCVACQERAHGTVLRPCQHRVLCEPCAASTPECPYCKGQPLPW 239
Cdd:cd16772   1 KKCIVCQERDRSIVLQPCQHYVLCEHCAASKPECPYCKTKILKW 44

Zinc finger, C3HC4 type (RING finger);

                          10        20        30        40
                  ....*....|....*....|....*....|....*....|..
gi 30794158   196 KQCVACQERAHGTVLRPCQHRVLCEPCA----ASTPECPYCK 233
Cdd:pfam13920   3 LLCVICLDRPRNVVLLPCGHLCLCEECAerllRKKKKCPICR 44

RING finger, HC subclass, found in inhibitor of apoptosis proteins (IAPs); IAPs are frequently overexpressed in cancer and associated with tumor cell survival, chemoresistance, disease progression, and poor prognosis. They function primarily as negative regulators of cell death. They regulate caspases and apoptosis through the inhibition of specific members of the caspase family of cysteine proteases. In addition, IAPs has been implicated in a multitude of other cellular processes, including inflammatory signalling and immunity, mitogenic kinase signalling, proliferation and mitosis, as well as cell invasion and metastasis. IAPs in this family includes cellular inhibitor of apoptosis protein c-IAP1 (BIRC2) and c-IAP2 (BIRC3), XIAP (BIRC4), BIRC7, and BIRC8, all of which contain three N-terminal baculoviral IAP repeat (BIR) domains that enable interactions with proteins, a ubiquitin-association (UBA) domain that is responsible for the binding of polyubiquitin (polyUb), and a C3HC4-type RING-HC finger at the carboxyl terminus that is required for ubiquitin ligase activity. The UBA domain is only absent in mammalian homologs of BIRC7. Moreover, c-IAPs contains an additional caspase activation and recruitment domain (CARD) between the UBA and C3HC4-type RING-HC domains. The CARD domain may serve as a protein interaction surface.

                        10        20        30        40
                ....*....|....*....|....*....|....*....|
gi 30794158 195 AKQCVACQERAHGTVLRPCQHRVLCEPCAASTPECPYCKG 234
Cdd:cd16510   1 EKLCKICMDREVNIVFLPCGHLVTCAQCAASLRKCPICRT 40

Modified RING finger, HC subclass (C3HC5-type), found in cell growth regulator with RING finger domain protein 1 (CGRRF1) and similar proteins; CGRRF1, also known as cell growth regulatory gene 19 protein (CGR19) or RING finger protein 197 (RNF197), functions as a novel biomarker to monitor endometrial sensitivity and response to insulin-sensitizing drugs, such as metformin, in the context of obesity. CGRRF1 contains a C-terminal modified C3HC5-type RING-HC finger, which 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.

                        10        20        30
                ....*....|....*....|....*....|....*...
gi 30794158 196 KQCVACQERAHGTVLRPCQHRVLCEPCAASTPECPYCK 233
Cdd:cd16787   1 KDCVVCQNAPVNRVLLPCRHACVCDECFKRLQRCPMCR 38

Modified RING finger, HC subclass (C3HC5-type), found in RING finger proteins, RNF26, RNF197 (CGRRF1), RNF156 (MGRN1), RNF157 and similar proteins; This subfamily corresponds to a group of RING finger proteins containing a modified C3HC5-type RING-HC finger, which 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. Cell growth regulator with RING finger domain protein 1 (CGRRF1), also known as cell growth regulatory gene 19 protein (CGR19) or RING finger protein 197 (RNF197), functions as a novel biomarker to monitor endometrial sensitivity and response to insulin-sensitizing drugs, such as metformin, in the context of obesity. RNF26 is an E3 ubiquitin ligase that temporally regulates virus-triggered type I interferon induction by increasing the stability of Mediator of IRF3 activation, MITA, also known as STING, through K11-linked polyubiquitination after viral infection and promoting degradation of IRF3, another important component required for virus-triggered interferon induction. Mahogunin ring finger-1 (MGRN1), also known as RING finger protein 156 (RNF156), is a cytosolic E3 ubiquitin-protein ligase that inhibits signaling 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. RNF157 is a cytoplasmic E3 ubiquitin ligase predominantly expressed in the brain. It is a homolog of the E3 ligase MGRN1. 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.

                        10        20        30        40
                ....*....|....*....|....*....|....*....|
gi 30794158 196 KQCVACQERAHGTVLRPCQHRVLCEPCAAS--TPECPYCK 233
Cdd:cd16649   1 GLCVVCLENPASVLLLPCRHLCLCEVCAKGlrGKTCPICR 40

Chromosome segregation ATPase Smc [Cell cycle control, cell division, chromosome partitioning];

                        10        20        30        40        50        60        70
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*
gi 30794158  76 ELARVRRQLDEAKRKIRQWEESWQQVKQACDAWQREAQEAKERARVADSDRQLALQRKEEVEAKVKQLQEELEGL 150
Cdd:COG1196 359 ELAEAEEALLEAEAELAEAEEELEELAEELLEALRAAAELAAQLEELEEAEEALLERLERLEEELEELEEALAEL 433

RING finger, HC subclass, found in mind bomb MIB1, MIB2, and similar proteins; MIBs are large, multi-domain E3 ubiquitin-protein ligases that promote ubiquitination of the cytoplasmic tails of Notch ligands. They are also responsible for TBK1 K63-linked ubiquitination and activation, promoting interferon production and controlling antiviral immunity. Moreover, MIBs selectively control responses to cytosolic RNA and regulate type I interferon transcription. Both MIB1 and MIB2 have similar domain architectures, which consist of two Mib-Herc2 domains flanking a ZZ zinc finger, a REP region including two tandem Mib repeats, an ANK region that spans ankyrin repeats, and a RNG region, where MIB1 and MIB2 contain three and two C3HC4-type RING-HC fingers, respectively. This model corresponds to the first RING-HC finger of MIB1 and MIB2, as well as the second RING-HC finger of MIB1.

                        10        20        30
                ....*....|....*....|....*....|....*...
gi 30794158 196 KQCVACQERAHGTVLRPCQHRVLCEPCAASTPECPYCK 233
Cdd:cd16519   1 EECRVCSDKKALVLFQPCGHVVACEECSLRMKKCLQCK 38

RING finger, HC subclass, found in caspases-8 and -10-associated RING finger protein CARP-1, CARP-2 and similar proteins; The CARP subfamily includes CARP-1 and CARP-2 proteins, both of which are E3 ubiquitin ligases that ubiquitinate apical caspases and target them for proteasome-mediated degradation. As a novel group of caspase regulators with a FYVE-type zinc finger domain, they do not localize to membranes in the cell and are involved in the negative regulation of apoptosis, specifically targeting two initiator caspases, caspase 8, and caspase 10. Moreover, they stabilize MDM2 by inhibiting MDM2 self-ubiquitination, as well as by targeting 14-3-3sigma for degradation. They work together with MDM2 to enhance p53 degradation, thereby inhibiting p53-mediated cell death. CARPs contain an N-terminal FYVE-like domain that can serve as a membrane-targeting or endosome localizing signal and a C-terminal C3HC4-type RING-HC finger domain.

                        10        20        30
                ....*....|....*....|....*....|....*.
gi 30794158 198 CVACQERAHGTVLRPCQHRVLCEPCAASTPECPYCK 233
Cdd:cd16500   3 CKICMDAAIDCVLLECGHMVTCTDCGKKLSECPICR 38

Uncharacterized conserved protein, contains a C-terminal ATPase domain [Function unknown];

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 30794158   77 LARVRRQLDEAKRKIRQWEESWQQVKQACDAWQREAQEAKERARVADSDRQLAlqrkeEVEAKVKQLQEELEGLGLSSlP 156
Cdd:COG4913  612 LAALEAELAELEEELAEAEERLEALEAELDALQERREALQRLAEYSWDEIDVA-----SAEREIAELEAELERLDASS-D 685

                         90       100       110       120
                 ....*....|....*....|....*....|....*....|.
gi 30794158  157 GLQSLGDISDiplpKLHSLQSKLRLDLEAVDGVIFQLRAKQ 197
Cdd:COG4913  686 DLAALEEQLE----ELEAELEELEEELDELKGEIGRLEKEL 722

RING finger, HC subclass, found in RNA-binding proteins of the evolutionarily-conserved MEX-3 family; MEX-3 phosphoproteins are found in vertebrates. They are mediators of post-transcriptional regulation in different organisms, and have been implicated in many core biological processes, including embryonic development, epithelial homeostasis, immune responses, metabolism, and cancer. They contain two K homology (KH) domains that provide RNA-binding capacity, and a C-terminal C3HC4-type RING-HC finger. They shuttle between the nucleus and the cytoplasm via the CRM1-dependent export pathway. The RNA-binding protein MEX-3 from nematode Caenorhabditis elegans is the founding member of the MEX-3 family. Due to the lack of a RING-HC finger, it is not included here.

                        10        20        30        40
                ....*....|....*....|....*....|....*....|..
gi 30794158 196 KQCVACQERAHGTVLRPCQHRVLCEPCA-----ASTPECPYC 232
Cdd:cd16518   1 RDCVVCFESEVVAALVPCGHNLFCMECAnriceKSDPECPVC 42

RING finger, HC subclass, found in Arabidopsis thaliana protein XB3 homolog 5 (XBAT35) and similar proteins; XBAT35, also known as ankyrin repeat domain and RING finger-containing protein XBAT35, or RING-type E3 ubiquitin transferase XBAT35, has no E3 ubiquitin-protein ligase activity observed when associated with the E2 enzyme UBC8 in vitro. It contains a typical C3HC4-type RING-HC finger.

                        10        20        30        40
                ....*....|....*....|....*....|....*....|....
gi 30794158 194 RAKQCVACQERAHGTVLRPCQHRVLCEPCA----ASTPECPYCK 233
Cdd:cd23129   1 QRDECVVCMDAPRDAVCVPCGHVAGCMSCLkalmQSSPLCPICR 44

RING finger, HC subclass, found in myosin regulatory light chain interacting protein (MYLIP) and similar proteins; MYLIP, also known as inducible degrader of the low-density lipoprotein (LDL)-receptor (IDOL), or MIR, is an E3 ubiquitin-protein ligase that mediates ubiquitination and subsequent proteasomal degradation of myosin regulatory light chain (MRLC), LDLR, VLDLR, and LRP8. Its activity depends on E2 ubiquitin-conjugating enzymes of the UBE2D family. MYLIP stimulates clathrin-independent endocytosis and acts as a sterol-dependent inhibitor of cellular cholesterol uptake by binding directly to the cytoplasmic tail of the LDLR and promoting its ubiquitination via the UBE2D1/E1 complex. The ubiquitinated LDLR then enters the multivesicular body (MVB) protein-sorting pathway and is shuttled to the lysosome for degradation. Moreover, MYLIP has been identified as a novel ERM-like protein that affects cytoskeleton interactions regulating cell motility, such as neurite outgrowth. The ERM proteins includes ezrin, radixin, and moesin, which are cytoskeletal effector proteins linking actin to membrane-bound proteins at the cell surface. MYLIP contains an ERM-homology domain and a C-terminal C3HC4-type RING-HC finger.

                        10        20        30
                ....*....|....*....|....*....|....*....
gi 30794158 195 AKQCVACQERAHGTVLRPCQHRVLCEPCAASTPECPYCK 233
Cdd:cd16523   2 AMLCMVCCEEEINSAFCPCGHMVCCESCAAQLQSCPVCR 40

second RING finger, HC subclass, found in mind bomb 1 (MIB1) and similar proteins; MIB1, also known as DAPK-interacting protein 1 (DIP-1) or zinc finger ZZ type with ankyrin repeat domain protein 2, is a large, multi-domain E3 ubiquitin-protein ligase that promotes ubiquitination of the cytoplasmic tails of Notch ligands, and thus plays an essential role in controlling metazoan development by Notch signaling. It is also involved in Wnt/beta-catenin signaling and nuclear factor (NF)-kappaB signaling, and has been implicated in innate immunity, neuronal function, genomic stability, and cell death. MIB1 contains an MZM region with two Mib-Herc2 domains flanking a ZZ zinc finger, a REP region including two tandem Mib repeats, an ANK region that spans ankyrin repeats, and a RNG region consisting of three C3HC4-type RING-HC fingers. This model corresponds to the second RING-HC finger.

                        10        20        30
                ....*....|....*....|....*....|....*...
gi 30794158 196 KQCVACQERAHGTVLRPCQHRVLCEPCAASTPECPYCK 233
Cdd:cd16725   1 EECVVCSDKKASVLFKPCGHMCACEGCAALMKKCVQCR 38

chromosome segregation protein SMC, common bacterial type; SMC (structural maintenance of chromosomes) proteins bind DNA and act in organizing and segregating chromosomes for partition. SMC proteins are found in bacteria, archaea, and eukaryotes. This family represents the SMC protein of most bacteria. The smc gene is often associated with scpB (TIGR00281) and scpA genes, where scp stands for segregation and condensation protein. SMC was shown (in Caulobacter crescentus) to be induced early in S phase but present and bound to DNA throughout the cell cycle. [Cellular processes, Cell division, DNA metabolism, Chromosome-associated proteins]

                           10        20        30        40        50        60        70
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*
gi 30794158     76 ELARVRRQLDEAKRKIRQWEESWQQVKQACDAWQREAQEAKERARVADSDRQLALQRKEEVEAKVKQLQEELEGL 150
Cdd:TIGR02168  720 ELEELSRQISALRKDLARLEAEVEQLEERIAQLSKELTELEAEIEELEERLEEAEEELAEAEAEIEELEAQIEQL 794

Uncharacterized conserved protein, contains a C-terminal ATPase domain [Function unknown];

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 30794158   76 ELARVRRQLDEAKRKIRQ----------WEESWQQ------VKQACDAW--QREAQEAKERARVADSDRQLALQRKEEVE 137
Cdd:COG4913  236 DLERAHEALEDAREQIELlepirelaerYAAARERlaeleyLRAALRLWfaQRRLELLEAELEELRAELARLEAELERLE 315

                         90
                 ....*....|...
gi 30794158  138 AKVKQLQEELEGL 150
Cdd:COG4913  316 ARLDALREELDEL 328

Modified RING finger, HC subclass (C3HC5-type), found in mahogunin RING finger protein 1 (MGRN1), RING finger protein 157 (RNF157) and similar proteins; MGRN1, also known as RING finger protein 156 (RNF156), is a cytosolic E3 ubiquitin-protein ligase that inhibits signaling 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. MGRN1 also 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 the brain. It is a homolog of the E3 ligase mahogunin ring finger-1 (MGRN1). 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. The C3HC5-type RING-HC finger 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.

                        10        20        30        40
                ....*....|....*....|....*....|....*....|..
gi 30794158 196 KQCVACQERAHGTVLRPCQHRVLCEPCAAS----TPECPYCK 233
Cdd:cd16789   1 SECVICLSDPRDTAVLPCRHLCLCSDCAEVlryqSNKCPICR 42

Chromosome segregation ATPase Smc [Cell cycle control, cell division, chromosome partitioning];

                        10        20        30        40        50        60        70
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*
gi 30794158  76 ELARVRRQLDEAKRKIRQWEESWQQVKQACDAWQREAQEAKERARVADSDRQLALQRKEEVEAKVKQLQEELEGL 150
Cdd:COG1196 247 ELEELEAELEELEAELAELEAELEELRLELEELELELEEAQAEEYELLAELARLEQDIARLEERRRELEERLEEL 321

RING finger, HC subclass, found in RNA-binding protein MEX3B; MEX3B, also known as RING finger and KH domain-containing protein 3 (RKHD3), or RING finger protein 195 (RNF195), is an RNA-binding phosphoprotein that localizes in P-bodies and stress granules, which are two structures involved in the storage and turnover of mRNAs. It regulates the spatial organization of the Rap1 pathway that orchestrates Sertoli cell functions. It has a 3' long conserved untranslated region (3'LCU)-mediated fine-tuning system for mRNA regulation in early vertebrate development such as anteroposterior (AP) patterning and signal transduction. MEX3B contains two K homology (KH) domains that provide RNA-binding capacity, and a C-terminal C3HC4-type RING-HC finger. Like other MEX-3 family proteins, MEX3B shuttles between the nucleus and the cytoplasm via the CRM1-dependent export pathway.

                        10        20        30        40
                ....*....|....*....|....*....|....*....|...
gi 30794158 195 AKQCVACQERAHGTVLRPCQHRVLCEPCA-----ASTPECPYC 232
Cdd:cd16721   4 SRDCSICFESEVIAALVPCGHNLFCMECAnriceKNEPQCPVC 46

RING finger, HC subclass, found in RNA-binding protein MEX3A; MEX3A, also known as RING finger and KH domain-containing protein 4 (RKHD4), is an RNA-binding phosphoprotein that localizes in P-bodies and stress granules, which are two structures involved in the storage and turnover of mRNAs. It has been implicated in the regulation of tumorigenesis. It controls the polarity and stemness of intestinal epithelial cells through the post-transcriptional regulation of the homeobox transcription factor CDX2, which plays a crucial role in intestinal cell fate specification, both during normal development and in tumorigenic processes involving intestinal reprogramming. Moreover, it exhibits a transforming activity when overexpressed in gastric epithelial cells. MEX3A contains two K homology (KH) domains that provide RNA-binding capacity, and a C-terminal C3HC4-type RING-HC finger. Like other MEX-3 family proteins, MEX3A shuttles between the nucleus and the cytoplasm via the CRM1-dependent export pathway.

                        10        20        30        40
                ....*....|....*....|....*....|....*....|...
gi 30794158 195 AKQCVACQERAHGTVLRPCQHRVLCEPCAA-----STPECPYC 232
Cdd:cd16720   2 GRDCMVCFESEVTAALVPCGHNLFCMECAVricerNEPECPVC 44

RING finger, HC subclass, found in Casitas B-lineage lymphoma (Cbl) proteins; The Cbl adaptor protein family contains a small class of RING-type E3 ubiquitin ligases with oncogenic activity, which is represented by three mammalian members, c-Cbl, Cbl-b and Cbl-c, as well as two invertebrate Cbl-family proteins, D-Cbl in Drosophila and Sli-1 in C. elegans. Cbl proteins function as potent negative regulators of various signaling cascades in a wide range of cell types. They play roles in ubiquitinating activated tyrosine kinases and targeting them for degradation. D-Cbl associates with the Drosophila epidermal growth factor receptor (EGFR) and overexpression of D-Cbl in the eye of Drosophila embryos inhibits EGFR-dependent photoreceptor cell development. Sli-1 is a negative regulator of the Let-23 receptor tyrosine kinase, an EGFR homolog, in vulva development. Cbl proteins in this subfamily consist of a highly conserved N-terminal half that includes a tyrosine-kinase-binding domain (TKB, also known as the phosphotyrosine binding PTB domain, composed of a four helix-bundle, a Ca2+ binding EF-hand and a highly variant SH2 domain) and a C3HC4-type RING-HC finger, both of which are required for Cbl-mediated downregulation of RTKs, and a divergent C-terminal region.

                        10        20        30        40
                ....*....|....*....|....*....|....*....|....*...
gi 30794158 191 FQLrakqCVACQERAHGTVLRPCQHrVLCEPCAAS-----TPECPYCK 233
Cdd:cd16502   1 FQL----CKICAENDKDVRIEPCGH-LLCTPCLTSwqdsdGQTCPFCR 43