UC San Diego

Premature mRNA polyadenylation, stop codon loss, or stop codon read-through results in decoding of poly(A) sequences which is a signal to induce ribosome-associated quality control events. ZNF598 is an important mammalian ribosome-associated E3 ligase that is involved in resolving stalled ribosomes attempting to translate poly(A)-containing sequences. ZNF598 regulates stall resolution via its ubiquitylation of two ribosomal proteins: RPS10 and RPS20. Our biochemical analysis of ZNF598 N-terminal domain truncations identifies the critical zinc fingers that are required for RPS10 and RPS20 ubiquitylation. Our results demonstrate that 1) RPS10 and RPS20 ubiquitylation, on their own, is insufficient to mediate proper ribosome stall resolution; 2) RPS10 and RPS20 ubiquitylation specificity depends on the length of the N- terminal region of ZNF598; 3) the N-terminal functional domains of ZNF598 are necessary but insufficient to trigger the poly(A)-induced stalling event.