Project description:Ubiquitin and ubiquitin-like proteins (UBLs) are directed to targets by cascades of E1, E2, and E3 enzymes. The largest ubiquitin E3 subclass consists of cullin-RING ligases (CRLs), which contain one each of several cullins (CUL1, -2, -3, -4, or -5) and RING proteins (RBX1 or -2). CRLs are activated by ligation of the UBL NEDD8 to a conserved cullin lysine. How is cullin NEDD8ylation specificity established? Here we report that, like UBE2M (also known as UBC12), the previously uncharacterized E2 UBE2F is a NEDD8-conjugating enzyme in vitro and in vivo. Biochemical and structural analyses indicate how plasticity of hydrophobic E1-E2 interactions and E1 conformational flexibility allow one E1 to charge multiple E2s. The E2s have distinct functions, with UBE2M/RBX1 and UBE2F/RBX2 displaying different target cullin specificities. Together, these studies reveal the molecular basis for and functional importance of hierarchical expansion of the NEDD8 conjugation system in establishing selective CRL activation. Mol Cell 33:483-495, 2009. Keywords: Comparison of gene expression profiles Ube2m and Ube2f are E2 enzymes that direct protein modification by NEDD8. Here we explore the specific functions of Ube2f and Ube2m by comparing gene expression profiles following knockdown of their function in NIH 3T3 cells. We used microarrays to detail the global programme of gene expression changes following knockdown of Ube2m and Ube2f in NIH 3T3 cells. NIH 3T3 cells were transduced with retroviral constructs containing shRNA directed against Ube2m or Ube2f. Three replicates of each condition were analyzed.
Project description:Ubiquitin and ubiquitin-like proteins (UBLs) are directed to targets by cascades of E1, E2, and E3 enzymes. The largest ubiquitin E3 subclass consists of cullin-RING ligases (CRLs), which contain one each of several cullins (CUL1, -2, -3, -4, or -5) and RING proteins (RBX1 or -2). CRLs are activated by ligation of the UBL NEDD8 to a conserved cullin lysine. How is cullin NEDD8ylation specificity established? Here we report that, like UBE2M (also known as UBC12), the previously uncharacterized E2 UBE2F is a NEDD8-conjugating enzyme in vitro and in vivo. Biochemical and structural analyses indicate how plasticity of hydrophobic E1-E2 interactions and E1 conformational flexibility allow one E1 to charge multiple E2s. The E2s have distinct functions, with UBE2M/RBX1 and UBE2F/RBX2 displaying different target cullin specificities. Together, these studies reveal the molecular basis for and functional importance of hierarchical expansion of the NEDD8 conjugation system in establishing selective CRL activation. Mol Cell 33:483-495, 2009. Keywords: Comparison of gene expression profiles
Project description:Protein neddylation modification is catalyzed by a neddylation activating enzyme (NAE, E1), an E2 conjugating enzyme and an E3 ligase. In various types of human cancers, the neddylation pathway was abnormally activated. Our previous study validated that neddylation E2 UBE2F is a promising lung cancer target. However, although NAE inhibitor MLN4924/pevonedistat is currently in few clinical trials for anticancer application, no small molecule was reported that targets UBE2F. Here, we report, for the first time, the discovery, via structure-based virtual screen and chemical optimization, of such a small molecule, designated as HA-9104. HA-9104 binds to UBE2F, reduces its protein levels, and consequently inhibits cullin-5 neddylation to inactivate CRL5 (cullin-RING ligase-5) ligase, leading to accumulation of CRL5 substrate, NOXA, to induce apoptosis. Moreover, HA-9104 appears to form the DNA adduct via its 7-azaindole group to induce DNA damage and G2/M arrest. Biologically, HA-9104 effectively suppresses the growth and survival of lung cancer cells and confers radiosensitization in both in vitro cell culture and in vivo xenograft tumor models. Taken together, our study discovered a small molecule HA-9104 that targets the UBE2F-CRL5 axis with anticancer activity alone or in combination with radiation.
Project description:Ubiquitin ligation is typically executed by hallmark E3 catalytic domains. Two such domains, "cullin-RING" and "RBR", are individually found in several hundred E3 ligases in humans, and collaborate with E2 enzymes to catalyze ubiquitylation. However, the vertebrate-specific CUL9 complex with RBX1 (also called ROC1), of interest due to its tumor suppressive interaction with TP53, uniquely encompasses both cullin-RING and RBR domains. Here, cryo-EM, biochemistry, and cellular assays elucidate a 1.8 MDa hexameric CUL9-RBX1 assembly. Within one dimeric subcomplex, an E2-bound RBR domain is activated by neddylation of its own cullin domain and positioning from the adjacent CUL9-RBX1 in trans. Our data show CUL9 as unique amongst RBX1-bound cullins in dependence on the metazoan-specific UBE2F neddylation enzyme, while the RBR domain protects it from deneddylation. Substrate ubiquitylation relies on both CUL9's neddylated cullin and RBR domains achieving self-assembled and chimeric cullin-RING/RBR E3 ligase activity.
Project description:Ubiquitin ligation is typically executed by hallmark E3 catalytic domains. Two such domains, "cullin-RING" and "RBR", are individually found in several hundred E3 ligases in humans, and collaborate with E2 enzymes to catalyze ubiquitylation. However, the vertebrate-specific CUL9 complex with RBX1 (also called ROC1), of interest due to its tumor suppressive interaction with TP53, uniquely encompasses both cullin-RING and RBR domains. Here, cryo-EM, biochemistry, and cellular assays elucidate a 1.8 MDa hexameric CUL9-RBX1 assembly. Within one dimeric subcomplex, an E2-bound RBR domain is activated by neddylation of its own cullin domain and positioning from the adjacent CUL9-RBX1 in trans. Our data show CUL9 as unique amongst RBX1-bound cullins in dependence on the metazoan-specific UBE2F neddylation enzyme, while the RBR domain protects from deneddylation. Mono-ubiquitylation of TP53 relies on both CUL9's neddylated cullin and RBR domains achieving self-assembled and chimeric cullin-RING/RBR E3 ligase activity.
Project description:We identified that Foxj1 is degraded by the ubiquitin proteasome system. Foxj1 protein is stabilized by the cullin-RING ligase inhibitor MLN4924. We evaluated global changes to ependymal cell culture gene expression profiles during MLN4924 treatment.
Project description:Cullin 4B (CUL4B) is a scaffold protein of the CUL4B-Ring E3 ligase (CRL4B) complex. Here, we found that CRL4B interacted with transcriptional corepressor complexes. Our results supporting CUL4B as a potential target of cancer therapy.
Project description:Here, we examined the interactions between PRMT6, poly(ADP-ribose) polymerase 1 (PARP1), and the cullin 4 B (CUL4B)-Ring E3 ligase (CRL4B) complex, to form a transcription-repressive complex that co-occupies the core clock gene PER3 promoter.
Project description:Covalent modifications of proteins with ubiquitin and ubiquitin-like molecules are instrumental to most, if not all biological processes. However, identifying the E3 ligase responsible for these modifications remains a major bottleneck in ubiquitin research. Here, we have developed an E2-thioester-driven identification (E2~dID) method for the targeted identification of substrates of specific E2 and E3 enzyme pairs. E2~dID exploits the central position of E2 conjugating enzymes in the ubiquitination cascade and provides in vitro generated biotinylated E2~ubiquitin thioester conjugates as the sole source for ubiquitination in extracto. This enables purification and identification of modified proteins by mass spectrometry under stringent conditions independently of the biological source of the extract. We demonstrate the sensitivity and specificity of E2-dID by identifying and validating substrates of the APC/C in human cells. Finally, performing E2~dID with SUMO in S. cerevisiae we show that E2-dID can be easily adapted to other ubiquitin-like modifiers and experimental models.
Project description:MicroRNAs (miRNAs) associate with Argonaute (AGO) proteins to direct widespread post-transcriptional gene repression. Although association with AGO typically protects miRNAs from nucleases, extensive pairing to some unusual target RNAs can trigger miRNA degradation. Here we found that this target-directed miRNA degradation (TDMD) required the ZSWIM8 Cullin-RING E3 ubiquitin ligase. This and other findings suggested and supported a mechanistic model of TDMD in which target-directed proteolysis of AGO by the ubiquitin–proteasome pathway exposes the miRNA for degradation. Moreover, loss-of-function studies indicated that the ZSWIM8 Cullin-RING ligase accelerates degradation of numerous miRNAs in cells of mammals, flies, and nematodes, thereby specifying the half-lives of most short-lived miRNAs. These results elucidate the mechanism of TDMD and expand the inferred role of TDMD in shaping miRNA levels in bilaterian animals.