
•SQSTM1/p62 is ubiquitylated by TRIM21 at K7 via K63-linkage •p62 K7 ubiquitylation prevents its dimerization and sequestration •TRIM21 negatively regulates Keap1 sequestration and anti-oxidative response •TRIM21 null liver and heart are protected from oxidative tissue damage
Protein (p62), which is supposed to act as an antioxidant to prevent cell damage, was found not work efficiently in laboratory mice with liver and heart disease that mimicked these conditions in humans. This caused oxidative stress and allowed the release of harmful molecules, called free radicals, which resulted in serious illness. One of the body’s first lines of defense, the cells antioxidant response system is supposed to prevent these harmful invaders from causing a domino effect and damaging other cells.
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![Synthesis of cyclotides. Cyclotides were assembled as linear precursors using FMOC chemistry, and cyclized using native chemical ligation. (1) Dawson’s resin containing di-Fmoc-3,4-diaminobenzoic acid (Dbz) as linker is the starting point. (2) Couplings are performed using microwave-assisted FMOC synthesis (asterisk marks the first amino acid; the last amino acid is a BOC-protected cysteine). (3) Acylation and activation of the resin bound Dbz-precursor to yield the N-acylurea peptide (Nbz-peptide). (4) Full deprotection and resin cleavage of the Nbz-peptide in one step (Ar, Aryl). Peptide cyclization (5a) via thioesterification, (5b) S, N-intramolecular acyl shift and native chemical ligation and (5c) oxidative folding to yield cyclotides with the native fold. Ribbon representation of a cyclotide (kalata B1, PDB ID code 1NB1) and sequence of [T20K]kalata B1 are shown. Cysteines, disulfide bonds (yellow), and intercysteine loops are indicated.](https://www.pnas.org/content/early/2016/03/22/1519960113/F1.medium.gif)



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