Cullin 7 Research Articles

Identification of MKRN1 as a second E3 ligase for Eag1 potassium channels reveals regulation via differential degradation

Mutations in the human gene encoding the neuron-specific Eag1 voltage-gated K+ channel are associated with neurodevelopmental diseases, indicating an important role of Eag1 during brain development. A disease-causing Eag1 mutation is linked to decreased protein stability that involves enhanced protein degradation by the E3 ubiquitin ligase cullin 7 (CUL7). The general mechanisms governing protein homeostasis of plasma membrane- and endoplasmic reticulum (ER)-localized Eag1 K+ channels, however, remain unclear. By using yeast two-hybrid screening, we identified another E3 ubiquitin ligase, makorin ring finger protein 1 (MKRN1), as a novel binding partner primarily interacting with the carboxyl-terminal region of Eag1. MKRN1 mainly interacts with ER-localized immature core-glycosylated, as well as nascent nonglycosylated, Eag1 proteins. MKRN1 promotes polyubiquitination and ER-associated proteasomal degradation of immature Eag1 proteins. Although both CUL7 and MKRN1 contribute to ER quality control of immature core-glycosylated Eag1 proteins, MKRN1, but not CUL7, associates with and promotes degradation of nascent, nonglycosylated Eag1 proteins at the ER. In direct contrast to the role of CUL7 in regulating both ER and peripheral quality controls of Eag1, MKRN1 is exclusively responsible for the early stage of Eag1 maturation at the ER. We further demonstrated that both CUL7 and MKRN1 contribute to protein quality control of additional disease-causing Eag1 mutants associated with defective protein homeostasis. Our data suggest that the presence of this dual ubiquitination system differentially maintains Eag1 protein homeostasis and may ensure efficient removal of disease-associated misfolded Eag1 mutant channels.

Cullin-7 (CUL7) is overexpressed in glioma cells and promotes tumorigenesis via NF-\u03baB activation

BackgroundCullin-7 (CUL7) is a member of the DOC domain-containing cullin family and is involved in the regulation of cell transformation. However, the clinical significance, potential mechanism and upstream regulators of CUL7 in malignant gliomas remain to be determined.MethodsExpression level data and clinical information were obtained via the Cancer Genome Atlas (TCGA) database, the Chinese Glioma Genome Atlas (CGGA) database, immunohistochemistry (IHC) and western blot analysis. Gene set enrichment analysis (GSEA) was used to explore the potential molecular mechanisms of CUL7. RNA silencing was performed using siRNA or lentiviral constructs in U87MG and U251 glioma cell lines and GSC267 glioma stem cells. CUL7 overexpression was performed using the GV141-CUL7 plasmid construct. In addition, overexpression of miR-3940-5p was performed and validated by quantitative real-time PCR (qRT-PCR). Cells were characterized in vitro or in vivo to evaluate their molecular status, cell proliferation, invasion, and migration by Cell Counting Kit (CCK)-8, EdU, flow cytometry, colony formation, Transwell and 3D tumour spheroid invasion assays. Coimmunoprecipitation (co-IP) and western blotting were performed to test the mechanisms of activation of the NF-κB signalling pathway.ResultsHigh CUL7 expression was associated with a high tumour grade, a mesenchymal molecular glioma subtype and a poor prognosis in patients. Gene silencing of CUL7 in U87MG and U251 cells significantly inhibited tumour growth, invasion and migration in vitro and in vivo. Western blot analysis revealed that cyclin-dependent kinase inhibitors and epithelial-mesenchymal transition (EMT) molecular markers changed under CUL7 silencing conditions. In contrast, CUL7 overexpression promoted tumour growth, invasion and migration. Gene set enrichment analysis (GSEA) and western blot analysis revealed that CUL7 was positively associated with the NF-κB pathway. Moreover, with coimmunoprecipitation assays, we discovered that CUL7 physically associated with MST1, which further led to ubiquitin-mediated MST1 protein degradation, which promoted activation of the NF-κB signalling pathway. Finally, CUL7 was found to be downregulated by miR-3940-5p, which suppressed the development of gliomas.ConclusionsOur findings indicate that CUL7 plays a significant role in promoting tumorigenesis via NF-κB activation and that it can be negatively regulated by miR-3940-5p in human gliomas. Furthermore, CUL7 might be a candidate molecular target for the treatment of glioma.

Chemosensory Event-Related Potentials and Power Spectrum could be A Possible Biomarker in 3M Syndrome Infants?

3M syndrome is a rare disorder that involves the gene cullin-7 (CUL7). CUL7 modulates odour detection, conditions the olfactory response (OR) and plays a role in the development of the olfactory system. Despite this involvement, there are no direct studies on olfactory functional effects in 3M syndrome. The purpose of the present work was to analyse the cortical OR through chemosensory event-related potentials (CSERPs) and power spectra calculated by electroencephalogram (EEG) signals recorded in 3M infants: two twins (3M-N) and an additional subject (3M-O). The results suggest that olfactory processing is diversified. Comparison of N1 and Late Positive Component (LPC) indicated substantial differences in 3M syndrome that may be a consequence of a modified olfactory processing pattern. Moreover, the presence of delta rhythms in 3M-O and 3M-N clearly indicates their involvement with OR, since the delta rhythm is closely connected to chemosensory perception, in particular to olfactory perception.

Abstract 4442: CUL7 promotes cancer cell survival through promoting Caspase-8 ubiquitination

Abstract The Cullin 7 (CUL7) gene encodes a member of the cullin family of E3 ubiquitin ligases. Accumulated evidence suggests that CUL7 is oncogenic. However, the mechanism by which CUL7 improves cancer cell survival has not been fully elucidated. Here, we reported that CUL7 confers anti-apoptotic functions by interacting with Caspase-8. CUL7 prevents Caspase-8 activation by promoting Caspase-8 modification with non-degradative polyubiquitin chains at K215. CUL7 knockdown sensitized cancer cells to TRAIL-induced apoptosis in vitro and in nude mice. These results suggest that CUL7 limits extrinsic apoptotic signaling by promoting Caspase-8 ubiquitination. Citation Format: Yanjie Kong, Zehua Wang, Zhongmei Zhou, Xiaoyu Mao, Ceshi Chen. CUL7 promotes cancer cell survival through promoting Caspase-8 ubiquitination [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4442.

CUL7 promotes cancer cell survival through promoting Caspase-8 ubiquitination.

The Cullin 7 (CUL7) gene encodes a member of the cullin family of E3 ubiquitin ligases. Accumulated evidence suggests that CUL7 is oncogenic. However, the mechanism by which CUL7 improves cancer cell survival has not been fully elucidated. Here, we reported that CUL7 confers anti-apoptotic functions by interacting with Caspase-8. CUL7 prevents Caspase-8 activation by promoting Caspase-8 modification with non-degradative polyubiquitin chains at K215. CUL7 knockdown sensitized cancer cells to TRAIL-induced apoptosis in vitro and in nude mice. These results suggest that CUL7 limits extrinsic apoptotic signaling by promoting Caspase-8 ubiquitination.

Cullin7 promotes epithelial‑mesenchymal transition of esophageal carcinoma via the ERK‑SNAI2 signaling pathway.

Cullin7 (CUL7) is a member of Cullin protein family and exhibits a tumor‑promoting role in several types of tumors, including breast, liver and ovarian. However, its roles in esophageal carcinoma (EC) have not yet been reported. In the present study, CUL7 expression in EC tissue was revealed to be significantly higher compared with nontumoral tissues, as detected by immunohistochemistry (IHC; P=0.000). χ2analysis confirmed that CUL7 expression was positively associated with invasion depth (P=0.000), lymph node involvement (P=0.033) and advanced clinical stage (P=0.000). Survival analysis demonstrated that CUL7 was positively associated with poor overall survival (P=0.001) and poor disease‑free survival (P=0.0019). An association of CUL7 with endothelial‑mesenchymal transition (EMT) was examined, and IHC results indicated that high CUL7 expression was associated with increased zinc finger protein SNAI2 (SNAI2) expression (P=0.000) and decreased E‑cadherin (P=0.000). Western blot analysis demonstrated that short hairpin RNA silencing CUL7 in EC1 cells increased epithelial (E)‑cadherin protein expression level, and decreased expression of Vimentin and SNAI2; cell migration was also reduced. Western blot analysis demonstrated that over expression of CUL7 in EC9706 cells increased Vimentin and SNAI2 protein expression, but decreased E‑cadherin expression, and the number of migratory cells. Investigation into the potential molecular mechanisms demonstrated that over expressing CUL7 in EC9706 cells stimulated the phosphorylation of ERK. Inhibiting ERK through treatment with U0126 significantly abrogated CUL7‑induced alterations in Vimentin, SNAI2 and E‑cadherin expression levels. Results from the present study demonstrated that CUL7 expression was associated with EC progression and poor prognosis. CUL7 may promote EMT via the ERK‑SNAI2 pathway in EC. These data may improve our understanding of the role of CUL7 in tumors and provide supporting evidence for the development of novel therapeutic targets for EC.

Support vector machine classifier for prediction of the metastasis of colorectal cancer.

Colorectal cancer (CRC) is one of the most common cancers and a major cause of mortality. The present study aimed to identify potential biomarkers for CRC metastasis and uncover the mechanisms underlying the etiology of the disease. The five datasets GSE68468, GSE62321, GSE22834, GSE14297 and GSE6988 were utilized in the study, all of which contained metastatic and non-metastatic CRC samples. Among them, three datasets were integrated via meta-analysis to identify the differentially expressed genes (DEGs) between the two types of samples. A protein-protein interaction (PPI) network was constructed for these DEGs. Candidate genes were then selected by the support vector machine (SVM) classifier based on the betweenness centrality (BC) algorithm. A CRC dataset from The Cancer Genome Atlas database was used to evaluate the accuracy of the SVM classifier. Pathway enrichment analysis was carried out for the SVM-classified gene signatures. In total, 358 DEGs were identified by meta-analysis. The top ten nodes in the PPI network with the highest BC values were selected, including cAMP responsive element binding protein 1 (CREB1), cullin 7 (CUL7) and signal sequence receptor 3 (SSR3). The optimal SVM classification model was established, which was able to precisely distinguish between the metastatic and non-metastatic samples. Based on this SVM classifier, 40 signature genes were identified, which were mainly enriched in protein processing in endoplasmic reticulum (e.g., SSR3), AMPK signaling pathway (e.g., CREB1) and ubiquitin mediated proteolysis (e.g., FBXO2, CUL7 and UBE2D3) pathways. In conclusion, the SVM-classified genes, including CREB1, CUL7 and SSR3, precisely distinguished the metastatic CRC samples from the non-metastatic ones. These genes have the potential to be used as biomarkers for the prognosis of metastatic CRC.

Comparative analysis of secretory factors from permanent- and deciduous-teeth periodontal ligament cells

ObjectiveStudies of regenerative therapies have focused on the paracrine effects of mesenchymal stem cells, but little has been revealed about the humoral factors of periodontal ligament (PDL) stem cells. The aim of this study was to identify and compare the secretory factors of human permanent- and deciduous-teeth PDL cells (P-PDL and D-PDL cells, respectively) in order to understand the characteristics of these cells and their potential applications in regenerative therapies. DesignConditioned media were collected from P-PDL and D-PDL cells (P-PDL-CM and D-PDL-CM, respectively). These media were analyzed with high-performance liquid-chromatography-coupled electrospray ionization tandem mass spectrometry and a cytokine membrane assay. In addition, Western blot analysis was performed to verify the differences between the two media. ResultsCytokines related to neurogenesis (NT-3 and NT-4) and angiogenesis-related cytokines (EGF and IGF-1) were identified in P-PDL-CM. The expression levels of immune-response-related cytokines (interleukins I, II, and IV) and secreted proteins related to tissue degradation and catalytic activities (matrix metallopeptidase 1 (MMP1), Proteasome subunit, alpha type, 1 (PSMA1), and cullin 7 (CUL7)) were higher in D-PDL-CM. Vasorin (VASN) was expressed more strongly in P-PDL-CM, but tudor domain containing 7 (TDRD7) was expressed more strongly in D-PDL-CM in Western blot analysis. ConclusionThe cytokine expressions of the two cell types showed different patterns, especially in neurogenesis and immune responses. P-PDL cells are more suitable candidates for applications in regenerative therapies.

Regulation of insulin receptor substrate-1 by mTORC2 (mammalian target of rapamycin complex 2)

mTOR (mammalian target of rapamycin) responds to the presence of nutrients, energy and growth factors to link cellular metabolism, growth and proliferation. The rapamycin-sensitive mTORC (mTOR complex) 1 activates the translational regulator S6K (S6 kinase), leading to increased protein synthesis in the presence of nutrients. On the other hand, the rapamycin-insensitive mTORC2 responds to the presence of growth factors such as insulin by phosphorylating Akt to promote its maturation and allosteric activation. We recently found that mTORC2 can also regulate insulin signalling at the level of IRS-1 (insulin receptor substrate-1). Whereas mTORC1 promotes IRS-1 serine phosphorylation that is linked to IRS-1 down-regulation, we uncovered that mTORC2 mediates its degradation. In mTORC2-disrupted cells, inactive IRS-1 accumulated despite undergoing phosphorylation at the mTORC1-mediated serine sites. Defective IRS-1 degradation was due to attenuated expression of the CUL7 (Cullin 7) ubiquitin ligase substrate-targeting sub-unit Fbw8. mTORC2 and Fbw8 co-localize at the membrane where mTORC2 phosphorylates Ser86 to stabilize Fbw8 and promotes its cytosolic localization upon insulin stimulation. Under conditions of chronic insulin exposure, inactive serine-phosphorylated IRS-1 and Fbw8 co-localize to the cytosol where the former becomes ubiquitylated via CUL7/Fbw8. Thus mTORC2 negatively feeds back to IRS-1 via control of Fbw8 stability and localization. Our findings reveal that, in addition to persistent mTORC1 signalling, increased mTORC2 signals can promote insulin resistance due to mTORC2-mediated degradation of IRS-1.

Anaesthesia and orphan disease

Anaesthesia and orphan disease

Cullin7: a new gene involved in liver carcinogenesis related to metabolic syndrome

BackgroundMetabolic syndrome (MS) is an emerging risk factor in hepatocellular carcinoma (HCC). HCC related to MS may occur either in advanced fibrosis or before the development of cirrhosis, suggesting involvement...

Maternal uniparental isodisomy and heterodisomy on chromosome 6 encompassing a CUL7 gene mutation causing 3M syndrome

We report a case of segmental uniparental maternal hetero- and isodisomy involving the whole of chromosome 6 (mat-hUPD6 and mat-iUPD6) and a cullin 7 (CUL7) gene mutation in a Japanese patient with 3M syndrome. 3M syndrome is a rare autosomal recessive disorder characterized by severe pre- and postnatal growth retardation that was recently reported to involve mutations in the CUL7 or obscurin-like 1 (OBSL1) genes. We encountered a patient with severe growth retardation, an inverted triangular gloomy face, an inverted triangle-shaped head, slender long bones, inguinal hernia, hydrocele testis, mild ventricular enlargement, and mild mental retardation. Sequence analysis of the CUL7 gene of the patient revealed a homozygous missense mutation, c.2975G>C. Genotype analysis using a single nucleotide polymorphism array revealed two mat-hUPD and two mat-iUPD regions involving the whole of chromosome 6 and encompassing CUL7. 3M syndrome caused by complete paternal iUPD of chromosome 6 involving a CUL7 mutation has been reported, but there have been no reports describing 3M syndrome with maternal UPD of chromosome 6. Our results represent a combination of iUPDs and hUPDs from maternal chromosome 6 involving a CUL7 mutation causing 3M syndrome.

Ubiquitin Ligase Cullin 7 Induces Epithelial-Mesenchymal Transition in Human Choriocarcinoma Cells

Germ line mutations of the ubiquitin ligase cullin 7 (CUL7) are linked to 3-M syndrome and Yakuts short stature syndrome, both of which are characterized by pre- and post-natal growth retardation. CUL7 knock-out mice show placental and embryonic defects similar to intrauterine growth retardation, suggesting a role of CUL7 in placentation. CUL7 was found in this study to be highly expressed in first trimester invasive human placental villi as well as in HTR8/SVneo and B6Tert cells, two cell lines derived from human first trimester trophoblast cells. However, CUL7 levels in term trophoblast cells or JEG-3 cells, which are derived from human choriocarcinoma but exhibit weak invasion capacity, were low or undetectable. Forced expression of CUL7 in JEG-3 cells induced cell morphological changes characteristic of epithelial-mesenchymal transition, which was accompanied by a complete loss of the epithelial markers E-cadherin and P-cadherin and a significant elevation of mesenchymal markers Vimentin and N-cadherin. JEG-3 cells expressing CUL7 exhibited enhanced cell migration and invasion. Conversely, CUL7-specific RNA interference in HTR8/SVneo cells resulted in increased E-cadherin expression and reduced cell migration and invasion. Furthermore, CUL7 expression down-regulated E-cadherin mRNA expression by up-regulating ZEB1 and Slug, two transcriptional repressors of E-cadherin. Finally, CUL7-induced loss of E-cadherin expression was partially reversed by treatment of CUL7-expressing cells with the proteasome inhibitor MG-132. These results suggest that the CUL7 E3 ligase is a key regulator in trophoblast cell epithelial-mesenchymal transition and placental development.

OR11,64 Growth hormone (GH) induces a dose-dependent, long-term increase in growth in pre-pubertal children with GH deficiency (GHD) without modifying the rate of initiation of puberty

restriction, maxillary hypoplasia, prominent heels and a variable incidence of skeletal abnormalities such as slender long bones and relatively tall vertebrae. Affected patients have a relatively poor growth response to growth hormone therapy. Nonsense and missense mutations in the genes encoding Obscurin-like 1 (OBSL1) and Cullin7 (CUL7) are known to cause 3M syndrome. There are, however some patients with well-defined 3-M syndrome but no mutation identified in either OBSL1 or CUL7. Aim: To assess cell proliferation, apoptosis and intracellular signal transduction responses to growth hormone (GH) and insulin-like growth factor-1 (IGF-I) in three 3-M patient cell lines: OBSL1 and CUL7 mutants and a cell line with no mutations in either gene. Methods: Dermal fibroblast cell lines were established from 2 unaffected children as controls and 3 patients, one with a nonsense mutation in CUL7 (c.4191delC p.H1379HfsX11), one with a nonsense mutation in OBSL1 (c.1273insAp.T425NfsX40) and one with 3-M syndrome but no identified mutation. Cell proliferation was assessed using a WST8 assay over 3 days and by measuring EdU incorporation at 24 hours. Apoptosis was measured using an ELISA for cleaved caspase 3 (CC-3), an essential enzyme for cell death. To assess GH and IGF-I signal transduction, control and patient fibroblasts were stimulated with GH (200ng/ml) and IGF-I (100ng/ml) with lysates taken at 0, 5, 15 and 60 minutes and immunoblotted for activation of ERK1/2, STAT5b, IRS-1 and Akt. Results: Both the WST8 assay and EdU incorporation showed basal cell proliferation to be decreased across all 3-M cell lines in comparison to controls (p < 0.01 for WST8 assay (OBSL1 mutant 65%, CUL7 mutant 64% and unknown mutant 78% compared to controls on day 3) and p < 0.01 for EdU incorporation (OBSL1mutant 43%, CUL7 mutant 24% and unknown mutant 25%)). There was no significant difference in the levels of CC-3 between patients and controls (p = 0.425, OBSL1 mutant 123%, CUL7 mutant 106% and unknown mutant 107% compared to controls). Following IGF-I stimulation, all three 3-M cell lines displayed normal IRS1 activation, but two showed reduced Akt activation when compared to controls (CUL7 mutant p < 0.01, unknownmutant p =0.024). Following GH stimulation, Stat5b and ERK1/2 activation was normal in OBSL1 and CUL7 mutant cell lines. Conclusions: 3-M syndrome is associated with reduced cell proliferation across all three cell lines but normal rates of apoptosis, even though each cell line carries a mutation in a different gene. However, only two of the three cell lines had reduced Akt activation in response to IGF-I stimulation. This suggests that disruption to different ‘upstream’ molecular pathways may lead into a common ‘downstream’ pathway that generates a consistent 3-M phenotype.

OR11,63 Growth hormone treatment has a positive effect on spine bone mineral density in young adults with childhood-onset growth hormone deficiency: a meta-analysis

restriction, maxillary hypoplasia, prominent heels and a variable incidence of skeletal abnormalities such as slender long bones and relatively tall vertebrae. Affected patients have a relatively poor growth response to growth hormone therapy. Nonsense and missense mutations in the genes encoding Obscurin-like 1 (OBSL1) and Cullin7 (CUL7) are known to cause 3M syndrome. There are, however some patients with well-defined 3-M syndrome but no mutation identified in either OBSL1 or CUL7. Aim: To assess cell proliferation, apoptosis and intracellular signal transduction responses to growth hormone (GH) and insulin-like growth factor-1 (IGF-I) in three 3-M patient cell lines: OBSL1 and CUL7 mutants and a cell line with no mutations in either gene. Methods: Dermal fibroblast cell lines were established from 2 unaffected children as controls and 3 patients, one with a nonsense mutation in CUL7 (c.4191delC p.H1379HfsX11), one with a nonsense mutation in OBSL1 (c.1273insAp.T425NfsX40) and one with 3-M syndrome but no identified mutation. Cell proliferation was assessed using a WST8 assay over 3 days and by measuring EdU incorporation at 24 hours. Apoptosis was measured using an ELISA for cleaved caspase 3 (CC-3), an essential enzyme for cell death. To assess GH and IGF-I signal transduction, control and patient fibroblasts were stimulated with GH (200ng/ml) and IGF-I (100ng/ml) with lysates taken at 0, 5, 15 and 60 minutes and immunoblotted for activation of ERK1/2, STAT5b, IRS-1 and Akt. Results: Both the WST8 assay and EdU incorporation showed basal cell proliferation to be decreased across all 3-M cell lines in comparison to controls (p < 0.01 for WST8 assay (OBSL1 mutant 65%, CUL7 mutant 64% and unknown mutant 78% compared to controls on day 3) and p < 0.01 for EdU incorporation (OBSL1mutant 43%, CUL7 mutant 24% and unknown mutant 25%)). There was no significant difference in the levels of CC-3 between patients and controls (p = 0.425, OBSL1 mutant 123%, CUL7 mutant 106% and unknown mutant 107% compared to controls). Following IGF-I stimulation, all three 3-M cell lines displayed normal IRS1 activation, but two showed reduced Akt activation when compared to controls (CUL7 mutant p < 0.01, unknownmutant p =0.024). Following GH stimulation, Stat5b and ERK1/2 activation was normal in OBSL1 and CUL7 mutant cell lines. Conclusions: 3-M syndrome is associated with reduced cell proliferation across all three cell lines but normal rates of apoptosis, even though each cell line carries a mutation in a different gene. However, only two of the three cell lines had reduced Akt activation in response to IGF-I stimulation. This suggests that disruption to different ‘upstream’ molecular pathways may lead into a common ‘downstream’ pathway that generates a consistent 3-M phenotype.

The CUL7 E3 Ubiquitin Ligase Targets Insulin Receptor Substrate 1 for Ubiquitin-Dependent Degradation

Recent genetic studies have documented a pivotal growth-regulatory role played by the Cullin 7 (CUL7) E3 ubiquitin ligase complex containing the Fbw8-substrate-targeting subunit, Skp1, and the ROC1 RING finger protein. In this report, we identified insulin receptor substrate 1 (IRS-1), a critical mediator of the insulin/insulin-like growth factor 1 signaling, as a proteolytic target of the CUL7 E3 ligase in a manner that depends on mammalian target of rapamycin and the p70 S6 kinase activities. Interestingly, while embryonic fibroblasts of Cul7-/- mice were found to accumulate IRS-1 and exhibit increased activation of IRS-1's downstream Akt and MEK/ERK pathways, these null cells grew poorly and displayed phenotypes reminiscent of those associated with oncogene-induced senescence. Taken together, our findings demonstrate a key role for the CUL7 E3 in targeting IRS-1 for degradation, a process that may contribute to the regulation of cellular senescence.

Clinical, molecular and histopathological features of short stature syndrome with novel CUL7 mutation in Yakuts: new population isolate in Asia

Background:In total, 43 patients having short stature syndrome in 37 Yakut families with autosomal recessive prenatal and postnatal nonprogressive growth failure and facial dysmorphism but with normal intelligence have been...

Identification of mutations in CUL7 in 3-M syndrome

Intrauterine growth retardation is caused by maternal, fetal or placental factors that result in impaired endovascular trophoblast invasion and reduced placental perfusion. Although various causes of intrauterine growth retardation have been identified, most cases remain unexplained. Studying 29 families with 3-M syndrome (OMIM 273750), an autosomal recessive condition characterized by severe pre- and postnatal growth retardation, we first mapped the underlying gene to chromosome 6p21.1 and then identified 25 distinct mutations in the gene cullin 7 (CUL7). CUL7 assembles an E3 ubiquitin ligase complex containing Skp1, Fbx29 (also called Fbw8) and ROC1 and promotes ubiquitination. Using deletion analysis, we found that CUL7 uses its central region to interact with the Skp1-Fbx29 heterodimer. Functional studies indicated that the 3-M-associated CUL7 nonsense and missense mutations R1445X and H1464P, respectively, render CUL7 deficient in recruiting ROC1. These results suggest that impaired ubiquitination may have a role in the pathogenesis of intrauterine growth retardation in humans.