Protein synthesis meets ABC ATPases: new roles for Rli1/ABCE1

Abstract

The essential NTPase Rli1/ABCE1 has been implicated in translation initiation, ribosome biogenesis, and human immunodeficiency virus capsid assembly. Two recent papers by the Krebber and Pestova groups —the former published in this issue of EMBO reports— suggest new important roles of Rli1/ABCE1 in translation termination and ribosome recycling in eukaryotes.

Figure 1

New roles of Rli1/ABCE1 in translation termination and ribosome recycling in eukaryotes. During termination, translating ribosomes contain peptidyl-tRNA (peptide is shown in dark blue and tRNA in dark red) in the P site and expose a stop codon in the A site. The stop codon is recognized by termination factor eRF1, which enters the ribosome together with eRF3-GTP. After GTP hydrolysis, catalysed by eRF3, the peptide is released from the peptidyl-tRNA with the help of eRF1. The point at which Rli1/ABCE1 binds to the ribosome is unknown, but the order shown is consistent with the effect of the factor on both termination and recycling. After NTP hydrolysis by Rli1/ABCE1, the 60S subunit and factors dissociate from the 40S subunit. Finally, tRNA and mRNA are released from the 40S subunit with the help of initiation factors (not shown). ABCE1, ATP-binding cassette, sub-family E member 1; eRF, eukaryotic release factor; Rli1, RNase L inhibitor 1.