Urm1: A Non-Canonical UBL.

Urm1 (ubiquitin related modifier 1) is a molecular fossil in the class of ubiquitin-like proteins (UBLs). It encompasses characteristics of classical UBLs, such as ubiquitin or SUMO (small ubiquitin-related modifier), but also of bacterial sulfur-carrier proteins (SCP). Since its main function is to modify tRNA, Urm1 acts in a non-canonical manner.

Molecular basis for the bifunctional Uba4-Urm1 sulfur-relay system in tRNA thiolation and ubiquitin-like conjugation.

The chemical modification of tRNA bases by sulfur is crucial to tune translation and to optimize protein synthesis. In eukaryotes, the ubiquitin-related modifier 1 (Urm1) pathway is responsible for the synthesis of 2-thiolated wobble uridine (U ). During the key step of the modification cascade, the E1-like activating enzyme ubiquitin-like protein activator 4 (Uba4) first adenylates and thiocarboxylates the C-terminus of its substrate Urm1.

The Uba4 domain interplay is mediated via a thioester that is critical for tRNA thiolation through Urm1 thiocarboxylation.

Eukaryotic ubiquitin-like proteins (UBLs) have evolved from prokaryotic sulfur-carrier proteins (SCPs). Ubiquitin related modifier 1 (Urm1) shares biochemical and structural features of UBLs and SCPs and is essential for 2-thiolation of cytoplasmic tRNA. This chemical modification of wobble uridine is highly conserved amongst species and is achieved via Urm1 thiocarboxylation by the non-canonical ubiquitin activating 4 enzyme (Uba4), which contains an E1- and a Rhodanese (RHD) domain.

Systematic Kinase Inhibitor Profiling Identifies CDK9 as a Synthetic Lethal Target in NUT Midline Carcinoma.

Kinase inhibitors represent the backbone of targeted cancer therapy, yet only a limited number of oncogenic drivers are directly druggable. By interrogating the activity of 1,505 kinase inhibitors, we found that BRD4-NUT-rearranged NUT midline carcinoma (NMC) cells are specifically killed by CDK9 inhibition (CDK9i) and depend on CDK9 and Cyclin-T1 expression. We show that CDK9i leads to robust induction of apoptosis and of markers of DNA damage response in NMC cells.

Elp3 links tRNA modification to IRES-dependent translation of LEF1 to sustain metastasis in breast cancer.

Quantitative and qualitative changes in mRNA translation occur in tumor cells and support cancer progression and metastasis. Posttranscriptional modifications of transfer RNAs (tRNAs) at the wobble uridine 34 (U34) base are highly conserved and contribute to translation fidelity. Here, we show that ELP3 and CTU1/2, partner enzymes in U34 mcms-tRNA modification, are up-regulated in human breast cancers and sustain metastasis.

Glutaredoxin GRXS17 Associates with the Cytosolic Iron-Sulfur Cluster Assembly Pathway.

Cytosolic monothiol glutaredoxins (GRXs) are required in iron-sulfur (Fe-S) cluster delivery and iron sensing in yeast and mammals. In plants, it is unclear whether they have similar functions. Arabidopsis (Arabidopsis thaliana) has a sole class II cytosolic monothiol GRX encoded by GRXS17 Here, we used tandem affinity purification to establish that Arabidopsis GRXS17 associates with most known cytosolic Fe-S assembly (CIA) components.

Targeting Drug Resistance in EGFR with Covalent Inhibitors: A Structure-Based Design Approach.

Receptor tyrosine kinases represent one of the prime targets in cancer therapy, as the dysregulation of these elementary transducers of extracellular signals, like the epidermal growth factor receptor (EGFR), contributes to the onset of cancer, such as non-small cell lung cancer (NSCLC). Strong efforts were directed to the development of irreversible inhibitors and led to compound CO-1686, which takes advantage of increased residence time at EGFR by alkylating Cys797 and thereby preventing toxic effects. Here, we present a structure-based approach, rationalized by subsequent computational analysis of conformational ligand ensembles in solution, to design novel and irreversible EGFR inhibitors based on a screening hit that was identified in a phenotype screen of 80 NSCLC cell lines against approximately 1500 compounds.

Fluorophore labeled kinase detects ligands that bind within the MAPK insert of p38α kinase.

The vast majority of small molecules known to modulate kinase activity, target the highly conserved ATP-pocket. Consequently, such ligands are often less specific and in case of inhibitors, this leads to the inhibition of multiple kinases. Thus, selective modulation of kinase function remains a major hurdle.