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Ubiquitin ligases are enzymes involved in the ligation step of ubiquitylation. Ubiquitin ligases bind the substrate protein and catalyse the transfer of ubiquitin from the cysteine of ubiquitin-conjugating enzymes to a lysine residue on the substrate protein.
The phytohormone auxin is sensed by SCFTIR1-AUX/IAA receptors leading to AUX/IAA repressor ubiquitylation and turnover. Here the authors show that IAA6 and IAA19 differ in their ubiquitylation and turnover dynamics, differentially contributing to auxin sensing and enabling discrimination of auxin concentrations.
Stress granules (SG) comprise aggregates of cellular messenger ribonucleoproteins (mRNPs) but how they form is unclear. Here, the authors identify NEDD4, an E3 ubiquitin ligase, as regulating the RNA binding protein NANOS2 and turnover of mRNP components, and so SG disassembly in spermatogonial stem cells.
MDM2 mutations that prevent E2–ubiquitin binding without altering RING domain structure lead to loss of E3-ligase activity, while the ability to limit p53 transcriptional activity is retained, allowing cells to respond more quickly to cellular stress.