Mechanistic dissection of premature translation termination induced by acidic residues-enriched nascent peptide

Ribosomes polymerize nascent peptides through repeated inter-subunit rearrangements between the classic and hybrid states. The peptidyl-tRNA, the intermediate species during translation elongation, stabilizes the translating ribosome to ensure robust continuity of elongation. However, the translation of acidic residue-rich sequences destabilizes the ribosome, leading to a stochastic premature translation cessation termed intrinsic ribosome destabilization (IRD), which is still ill-defined. Here, we dissect the molecular mechanisms underlying IRD in Escherichia coli. Reconstitution of the IRD event reveals that (1) the prolonged ribosome stalling enhances IRD-mediated translation discontinuation, (2) IRD depends on temperature, (3) the destabilized 70S ribosome complex is not necessarily split, and (4) the destabilized ribosome is subjected to peptidyl-tRNA hydrolase-mediated hydrolysis of the peptidyl-tRNA without subunit splitting or recycling factors-mediated subunit splitting. Collectively, our data indicate that the translation of acidic-rich sequences alters the conformation of the 70S ribosome to an aberrant state that allows the noncanonical premature termination. [Display omitted] •Temperature and elongation stalling affect the intrinsic destabilization of the ribosome•Intrinsically destabilized ribosomes are not necessarily split into subunits•Pth hydrolyzes the peptidyl-tRNA within the destabilized 70S without ribosome splitting•Ribosome recycling factors can split the destabilized 70S ribosome with peptidyl-tRNA Chadani et al. characterize the molecular determinants of acidic-rich nascent chain-induced intrinsic ribosome destabilization (IRD) in Escherichia coli. IRD is affected by temperature, elongation stalling, and translation factors. IRD prematurely terminates translation through two distinct mechanisms: either Pth-mediated hydrolysis of peptidyl-tRNA within 70S complex or splitting facilitated by recycling factors.