Project description:It has been recognized that BRCA1, in the form of the BRCA1/BARD1 heterodimer, acting as an ubiquitin E3 ligase offered a possible mechanism to explain its pleiotrophic nature of BRCA1 activity. Our observation that mice lacking BRCA1 enzymatic activity are viable apart from male sterility was unexpected. Our results suggest that the E3 ligase activity of BRCA1 is largely dispensable for normal development and is not essential for all BRCA1 functions. Thus, many of the known and unknown functions of BRCA1 are likely to be mediated independent of its ability to catalyze ubiquitination. The genome copy number patterns were studied on the mice tumors that lacks E3 ubiqitin ligase activity of BRCA1 and were compared to copy number profile of mice lacking p53 and both brca1 and p53. Array CGH was performed using Agilent mouse CGH microarray 244K kit. Genomic DNA isolated from tumor tissue and its corresponding mouse tail were labelled with two different dyes and hybridized simultaneously on to microarray slides to perform comparitive genomic hybridization.
Project description:It has been recognized that BRCA1, in the form of the BRCA1/BARD1 heterodimer, acting as an ubiquitin E3 ligase offered a possible mechanism to explain its pleiotrophic nature of BRCA1 activity. Our observation that mice lacking BRCA1 enzymatic activity are viable apart from male sterility was unexpected. Our results suggest that the E3 ligase activity of BRCA1 is largely dispensable for normal development and is not essential for all BRCA1 functions. Thus, many of the known and unknown functions of BRCA1 are likely to be mediated independent of its ability to catalyze ubiquitination. The genome copy number patterns were studied on the mice tumors that lacks E3 ubiqitin ligase activity of BRCA1 and were compared to copy number profile of mice lacking p53 and both brca1 and p53.
Project description:Regulation of metabolic enzymes through degradation by the ubiquitin-proteosome system regulation is essential towards maintenance of cellular homeostasis. Our approach directly addresses a problem in the field; linking metabolic signal to an E3 ligase response. We employ active E3 ligase profiling coupled with broad MS-based screening, to reveal the changes in the proteome and E3 ligase-ome in response to the starvation or excess of a specific metabolite. We then use computationally driven strategies to connect these responses before in vitro and in cellulo reconstitution. The application of this strategy on cysteine metabolism led to our finding of LRRC58 mediated control of CDO1 degradation. Through reconstitution of this system, we also reveal that endogenous CDO1 degradation by LRRC58 is distinct from degradation induced by a molecular glue. Additionally, we have visualized CDO1 ubiquitylation by an LRRC58 CRL through cryo-EM, demonstrating the structural basis for CDO1 targeting by LRRC58.
Project description:To identify substrates of the ubiquitinating E3 enzyme Rsp5 we applied purified Rsp5 to duplicate protein arrays. The Rsp proteins were expressed as fusion proteins to GST. We used as a control Ubr1, a RING domain containing E3 ligase We analyzed Rsp5 from S.cerevisiae on duplicate arrays, with four control chips, two without Rsp5 and two with Ubr1.
Project description:Inhibiton of NSD2 by shRNA induces K562 differentiation via increasing erythroid specfic lineage factors The human myelogenous leukemic cell line, K562 undergoes erythroid differentiation by exposure to hemin. Here, we uncovered NSD2 as an innate erythroid differentiation-related factor through the genome-wide CRISPR library screening and explored the regulatory role of NSD2 during myeloid leukemia cell differentiation. We found that NSD2 stability was disrupted by poly-ubiquitination in differentiated K562 cells. Proteomic analysis revealed interaction between NSD2 and an E3 ubiquitin ligase, BRCA1 which ubiquitylates NSD K292 residue. Depletion of BRCA1 stabilized NSD2 protein and suppressed K562 cell differentiation. Furthermore, BRCA1 protein level was decreased in bone marrow tumor, while NSD2 level was elevated. Surprisingly, among BRCA1 mutation(s) discovered in lymphoma patients, BRCA1 K1183R prevented its translocation into the nucleus and did not reduce NSD2 protein level in hemin-treated K562 cells and eventually disrupted cell differentiation. Our results indicated that regulation of NSD2 stability by BRCA1-mediated ubiquitination as a potential therapeutic target process in multiple myeloma.
Project description:The TRIM37 gene is mutatedin Mulbery nanism, a rare autosomal recessive disorder, and is in the 17q23 chromosomal region that is amplified in up to ~40% of breast cancers. Trim37 contains a RING finger domain, a hallmark of E3 ubiquitin ligases, but the protein substrate(s) of Trim37 is unknown. Mono-ubiquitination of histone H2A is a chromatin modification associated with transcriptional repression and here we report that Trim37 is an H2A ubiquitin ligase. Genome-wide Chip-CHIP experiments indicate that in human breast cancer cells containing amplified 17q23, Trim37 is bound to the promoters of many tumor suppressor genes. RNA interference (RNAi)-mediated knockdown of Trim37 results in loss of ubiquitinated H2A, dissociation of PRC1 and PRC2, and transcriptional reactivation of silenced genes. Knockdown of Trim37 in human breast cancer cells containing amplified 17q23 substantially decreases tumor growth in mouse xenografts. Collectively, our results reveal Trim37 as a new H2A ubiquitin ligase that is overexpressed in a subset of breast cancers and redirects PRC2 to silence tumor suppressors and other genes resulting in oncogenesis. Identification of TRIM37 Binding targets in MCF7 cells from the two replicate experiments
Project description:The E3 ubiquitin ligase HUWE1 modifies a diverse network of substrate proteins by ubiquitination, through which it regulates various intracellular processes and contributes to both oncogenic and tumour suppressor mechanisms in different cancer contexts. Here, by analysing human lung adenocarcinoma (LUAD) patient samples, we reveal that HUWE1 protein expression is commonly upregulated in LUAD tumours compared to normal adjacent lung tissue and that this increase is associated with tumour stage. Using multiple, independent murine models of LUAD initiation and growth, we identify that Huwe1 is essential for mutant Kras-induced lung tumour development and reveal a novel, p53-independent requirement for Huwe1 in LUAD. Mechanistically, we demonstrate induction of senescence following HUWE1 depletion - characterised by impaired proliferation, an atypical cell cycle distribution, emergence of morphologically abnormal enlarged cells, increased β-galactosidase activity, and transcriptional reprogramming associated with inflammatory senescence-associated secretory phenotype (SASP) signalling and NFκB activation. Together, these data highlight a crucial role for HUWE1 in mutant Kras-induced LUAD tumorigenesis and in the continued growth and proliferation of established LUAD cells, confirming HUWE1 as a rational therapeutic target for LUAD.
Project description:To identify substrates of the ubiquitinating E3 enzyme Rsp5 we applied purified Rsp5 to duplicate protein arrays. The Rsp proteins were expressed as fusion proteins to GST. We used as a control Ubr1, a RING domain containing E3 ligase
Project description:Deficiencies in the BRCA1 tumor suppressor gene are the main cause of hereditary breast and ovarian cancer. BRCA1 is involved in the Homologous Recombination DNA repair pathway, and, together with BARD1, forms a heterodimer with ubiquitin E3 activity. The relevance of the BRCA1/BARD1 ubiquitin E3 activity for tumor suppression and DNA repair remains controversial and most efforts aimed to identify BRCA1/BARD1 ubiquitination substrates rely on indirect evidence. Here, we observed that the BRCA1/BARD1 ubiquitin E3 activity was not required for Homologous Recombination or resistance to Olaparib. Using TULIP2 methodology, which enables the direct identification of E3-specific ubiquitination substrates, we identified substrates for BRCA1/BARD1. We found that PCNA is ubiquitinated by BRCA1/BARD1 in unperturbed conditions independently of RAD18. PCNA ubiquitination by BRCA1/BARD1 avoids the formation of ssDNA gaps during DNA replication and promotes continuous DNA synthesis. These results address the controversy about the function of BRCA1/BARD1 E3 activity in Homologous Recombination.