Initiation Factor 3 (if3) Does Not Have Any Role in the Release of Messenger Rna and Transfer Rna from the Post-Termination Complex During the Ribosome Recycling Reaction Catalyzed by Ef-G/Gtp and Rrf (ribosome Recycling Factor)

At the end of translation of an ORF, the ribosome meets the termination codon and peptides are released by release factors 1, 2 and 3. The resulting post-termination complex (PoTC) is characterized to have one tRNA and mRNA per ribosome. We showed that it is disassembled by RRF and EF-G/GTP into mRNA, tRNA, and subunits (JBC, 1973, 248, 7580). On the other hand, others claimed that RRF and EF-G split the ribosome but do not release mRNA or tRNA. IF3 was claimed to be necessary to release mRNA and/or tRNA from the complex of 30S/tRNA/mRNA. This wrong conclusion is due to the use of short ORF with strong SD sequence (Mol Cell., 2005, 18, 675; Mol Cell., 2005, 18, 403). We use more natural PoTC which is free of the influence of the SD sequence, and show here that IF3 has no role in the release of mRNA and tRNA from the PoTC. We (RNA, 2005, 8, 1317) and others showed that splitting of subunits occurs due to RRF and EF-G. It has been known that IF3 prevents association of subunits. However, its effect on the rate of ribosomal splitting by EF-G/RRF remains to be elucidated. In this paper, we will present the results which shed lights on this question.