Project description:Reversibility of protein ubiquitylation play essential roles in cellular protein homeostasis. How substrates stabilized by deubiquitylation are directed for degradation remains largely elusive. Here, we show that the branched ubiquitin chains promote the degradation of the deubiquitylase (DUB) OTUD5. OTUD5 is sequentially modified by TRIP12 and UBR5, E3s specific for the K29 and K48 linkages, respectively, resulting in the conjugation of K29/K48 branched ubiquitin chains. The TRIP12-OTUD5 antagonism regulates TNF--induced NF-B signaling. Mechanistically, while OTUD5 readily cleaves K48-linkages, K29-linkages are resistant against OTUD5 activity. Consequently, K29-linkages overcome OTUD5 DUB activity to facilitate UBR5-dependent K48-linked chain branching. Regarding generality, this mechanism adopts to other TRIP12 substrates associated with OTUD5. These results uncover a cellular unique strategy in which the sequential addition of DUB-resistant and proteasome-targeting ubiquitin linkages efficiently promote degradation of substrates protected by deubiquitylation, underscoring the role of branched ubiquitin chains in the quality control of hard-to-degrade substrates.
Project description:In Saccharomyces cerevisiae histone H2B is ubiquitylated at lysine 123. The SAGA complex component, Ubp8, is one of two proteases that remove this ubiquitin moiety. We analyzed gene expression in a strain containing a variant of histone H2B with lysine 123 converted to arginine to address the mechanisms by which ubiquitylation and deubiquitylation of histone H2B affects gene expression. We show that changes in gene expression observed upon deletion of ubp8 are suppressed by htb1K123R. This provides genetic evidence that Ubp8 alters gene expression through deubiquitylation of histone H2B. Second, microarray analyses of the htb1K123R strain show that loss of histone ubiquitylation results in a two-fold or greater change in expression of ~1.5% of the protein coding genes with greater than two-thirds increasing. For genes in which ubiquitylation represses expression, ubiquitylation principally acts through its effects on histone methylation. In contrast, decreased expression of the CWP1 gene was not paralleled by deletions of the methyltransferase components Swd3, Set2 or Dot1 and is thus likely independent of methylation. Finally, by comparing gene expression changes in the htb1K123R strain with those in a strain deleted for rad6, we conclude that lysine 123 affects transcription primarily because of its being a site of ubiquitylation. Keywords: yeast, histone ubiquitylation, Ubp8, gene expression, genetic modification, histone H2B Two dye-swapped, biological replicate experiments were performed for yeast strains CY1272(Htb1_K123R;htb2_delta0), BY10809(ubp8_delta0) and CY1383(Htb1_K123R;htb2_delta0;ubp8_delta0) with reference to BY4742(wt). Three biological replicates, including one dye-swap experiment, were performed comparing CY1272(Htb1_K123R;htb2_delta0) to BY13026(htb2_delta0).
Project description:The project aims to look at mutational signatures in a rare inherited skin tumour syndrome called CYLD cutaneous syndrome. These patients develop multiple skin tumours that are seen at sun exposed and sun protected sites. We plan to carry out WGS on carefully curated tumours from such patients. We then plan to analyse this data for mutational signatures, comparing this between sun exposed and sun protected sites.
Project description:In Saccharomyces cerevisiae histone H2B is ubiquitylated at lysine 123. The SAGA complex component, Ubp8, is one of two proteases that remove this ubiquitin moiety. We analyzed gene expression in a strain containing a variant of histone H2B with lysine 123 converted to arginine to address the mechanisms by which ubiquitylation and deubiquitylation of histone H2B affects gene expression. We show that changes in gene expression observed upon deletion of ubp8 are suppressed by htb1K123R. This provides genetic evidence that Ubp8 alters gene expression through deubiquitylation of histone H2B. Second, microarray analyses of the htb1K123R strain show that loss of histone ubiquitylation results in a two-fold or greater change in expression of ~1.5% of the protein coding genes with greater than two-thirds increasing. For genes in which ubiquitylation represses expression, ubiquitylation principally acts through its effects on histone methylation. In contrast, decreased expression of the CWP1 gene was not paralleled by deletions of the methyltransferase components Swd3, Set2 or Dot1 and is thus likely independent of methylation. Finally, by comparing gene expression changes in the htb1K123R strain with those in a strain deleted for rad6, we conclude that lysine 123 affects transcription primarily because of its being a site of ubiquitylation. Keywords: yeast, histone ubiquitylation, Ubp8, gene expression, genetic modification, histone H2B
Project description:Histone post-translational modifications (PTMs) play a critical role in chromatin regulation. It has been proposed that these PTMs form localized “codes” that are read by specialized domains (reader domains) in chromatin associated proteins (CAPs) to regulate downstream function. Substantial effort has been made to define [CAP - histone PTM] specificity, and in doing so to decipher the histone code. However, this has largely been done using a reductive approach of isolated reader domains and histone peptides, with the assumption that PTM readout is unaffected by any higher order considerations. Here we show that histone PTM specificity is in fact dependent on nucleosomal context, necessitating we re-define the ‘histone code’ concept and further interrogate it at the nucleosomal level.
Project description:Targeted protein degradation is a powerful tool in determining the function of specific proteins or protein complexes. We fused nanobodies to SPOP, an adaptor protein of the Cullin-RING E3 ubiquitin ligase complex, resulting in rapid ubiquitination and subsequent proteasome-dependent degradation of specific nuclear proteins in mammalian cells and zebrafish embryos. This approach is easily modifiable, as substrate specificity is conferred by an antibody domain that can be adapted to target virtually any protein.
Project description:To survive under adverse conditions, plants form stress granules (SGs) to temporally store mRNA and halt translation as a primary response. Dysregulation in SG disassembly can have detrimental effects on plant survival after stress release, yet the underlying mechanism remains poorly understood in plants. Using Arabidopsis as a model system, we demonstrated that the AP-3 subunit AP-3β participates in heat response independently of its conventional role in vacuolar transport. We also discovered that AP-3β serves as an adaptor to recruit the 19S regulatory particle (RP) of the proteasome to SGs upon heat induction. Notably, the 19S RP promotes SG disassembly through RP-associated deubiquitylation, independent of its proteolytic activity. This deubiquitylation process of SG components is crucial for translation reinitiation and growth recovery after heat release. Our findings shed light on the non-proteolytic function of the 19S RP in regulating SGs dynamics and provide insights into a non-degradation mechanism for cellular adaptation to environmental stresses
Project description:Two-dimensional patterning of the follicular epithelium in Drosophila oogenesis is required for the formation of three-dimensional eggshell structures. Our analysis of a large number of published gene expression patterns in the follicle cells suggests that they follow a simple combinatorial code based on six spatial building blocks and the operations of union, difference, intersection, and addition. The building blocks are related to the distribution of inductive signals, provided by the highly conserved epidermal growth factor receptor and Decapentaplegic (DPP) pathways. We demonstrate the validity of the code by testing it against a set of patterns obtained in a large-scale transcriptional profiling experiment. Using the proposed code, we distinguish 36 distinct patterns for 81 genes expressed in the follicular epithelium and characterize their joint dynamics over four stages of oogenesis. The proposed combinatorial framework allows systematic analysis of the diversity and dynamics of two-dimensional transcriptional patterns and guides future studies of gene regulation. Keywords: EGFR, BMP, gain/loss-of-function