E3 ubiquitin ligases MKRN1/2 and RNF214 are required for efficient stress granule clearance

Stress granules (SGs) are dynamic biomolecular condensates formed by proteins, RNAs, and ribonucleoprotein complexes in response to various forms of stress. Although SGs play a protective role in stress adaptation, impaired SG disassembly during stress recovery has been implicated in aging and neurodegeneration. The efficient clearance of SGs requires the ubiquitin-proteasome system, but specific E3 ubiquitin ligases (E3s) involved remain poorly characterized. In this study, we identify RING finger protein 214 (RNF214) and the Makorins MKRN1 and MKRN2 as key regulators of SG turnover. All three E3s associate with arsenite- and heat-induced SGs, and their depletion compromises SG clearance. Loss of MKRN1/2, but not RNF214, is linked to impaired proteasomal protein degradation: It disrupts K48-linked polyubiquitylation of SGs, prevents 26S proteasome recruitment to SGs, results in the accumulation of misfolded proteins at SGs, and generates persistent SGs that are targets for granulophagy. Co-depletion of MKRN1/2 and RNF214 causes an additive SG clearance defect, indicating that these E3s control SG disassembly through distinct, proteasome-dependent and -independent functions, respectively.