Dissociation by Pelota, Hbs1 and ABCE1 of mammalian vacant 80S ribosomes and stalled elongation complexes

Abstract

No-go decay (NGD) and non-stop decay (NSD) are eukaryotic surveillance mechanisms that target mRNAs on which elongation complexes (ECs) are stalled by, for example, stable secondary structures (NGD) or due to the absence of a stop codon (NSD). Two interacting proteins Dom34(yeast)/Pelota(mammals) and Hbs1, which are paralogues of eRF1 and eRF3, are implicated in these processes. Dom34/Hbs1 were shown to promote dissociation of stalled ECs and release of intact peptidyl-tRNA. Using an in vitro reconstitution approach, we investigated the activities of mammalian Pelota/Hbs1 and report that Pelota/Hbs1 also induced dissociation of ECs and release of peptidyl-tRNA, but only in the presence of ABCE1. Whereas Pelota and ABCE1 were essential, Hbs1 had a stimulatory effect. Importantly, ABCE1/Pelota/Hbs1 dissociated ECs containing only a limited number of mRNA nucleotides downstream of the P-site, which suggests that ABCE1/Pelota/Hbs1 would disassemble NSD complexes stalled at the 3 0 -end, but not pre-cleavage NGD complexes stalled in the middle of mRNA. ABCE1/Pelota/Hbs1 also dissociated vacant 80S ribosomes, which stimulated 48S complex formation, suggesting that Pelota/Hbs1 have an additional role outside of NGD.

The biological regulation of ABCE1

“…Finally, ATP hydrolysis is required to release ABCE1 protein from the 30S subunit to initiate a new translation cycle (9). Not only could ABCE1 protein dissociate post-termination complexes, which is obtained with eRF1 and eRF3, but could also accompany with Pelota and Hbs, which are paralogues of eRF1 and eRF3, to induce dissociation of elongation complexes (8). Remarkably, a structural basis and a universal mechanistic model for eukaryotic and archaeal ribosome recycling has been established, in which ABCE1 protein coordinates translation termination with recycling: In the recognition stage, eRF1: eRF3 or Pelota/Dom34: Hbs1 are delivered to stalled ribosomes or pretermination complexes.…”

“…The protein was then demonstrated as a host factor essential for assembly of primate lentivirus capsids, especially for HIV-1 (5,6). Recent evidence indicated new important roles of ABCE1 protein in translation initiation, elongation, termination, and ribosome recycling in eukaryotes (7)(8)(9).…”

Rustless translation

“…Analogous to the eRF1-eRF3 system in normal translation termination, the stalled ribosomes are recognized by Pelota (Dom34 in yeast, a homolog of eRF1) and Hbs1 (a homolog of eRF3), resulting in the release of peptidyl-tRNA (Saito et al , 2010 ;Tsuboi et al , 2012 ). ABCE1 also works together with Dom34/Pelota, suggesting that ABCE1 is a universal ribosome splitting/recycling factor in eukaryotic and archaeal translation termination that works not only release factor dependent termination but also on Dom34/Pelota dependent recognition of stalled ribosomes (Pisareva et al , 2011 ) (Figure 3).…”

“…Subsequent studies extended the role of ABCE1 also to the recycling of stalled elongation complexes (Pisareva et al , 2011 ): ribosome elongation complexes that are stalled for instance at mRNA with secondary structures or at mRNAs that lack a proper stop codon trigger no-go decay or nonstop decay surveillance pathways, upon which malfunctioning mRNAs are degraded in eukaryotes (van Hoof and Wagner , 2011 ). Analogous to the eRF1-eRF3 system in normal translation termination, the stalled ribosomes are recognized by Pelota (Dom34 in yeast, a homolog of eRF1) and Hbs1 (a homolog of eRF3), resulting in the release of peptidyl-tRNA (Saito et al , 2010 ;Tsuboi et al , 2012 ).…”

ABCE1 is essential for S phase progression in human cells

“…22 In addition to canonical termination, ABCE1 dissociates stalled and vacant ribosomes acting in quality control mechanisms during mRNA translation and ribosome biogenesis, and in regulation of available ribosome pool. [23][24][25] Moreover, ABCE1 recycling activity may control non-canonical 3 0 -UTR translation on stalled ribosomes during stress. 26 The function of ABCE1 in ribosome recycling is conserved in archaea, in contrast to the initiation stage lacking the eukaryotic homologues of eIF3 and eIF5.…”