Coordinated translation initiation determines -1 programmed ribosomal frameshifting efficiency of chromosomal genes to impact on cell fitness.

The conserved -1 programmed ribosomal frameshifting (-1PRF), essential for eubacteria and RNA viruses, is thought to be exclusively regulated during translation elongation. One of the two required -1PRF cis-acting elements is a frameshifting stimulatory element (FSE), which pauses the elongating ribosome to stimulate -1PRF and is consecutively deformed. Consequently, the remaining hypothesis involves the coordination between translation initiation and FSE reformation, which facilitates the -1PRF events in trailing ribosomes. Here, we create a system that allows a tunable translation initiation rate based on the MS2 bacteriophage coat protein translation initiation hairpin to assess this conjecture. We discovered a conserved negative correlation between translation initiation rate and -1PRF efficiency in eubacteria and mammalian cells. Mechanistic exploration using Escherichia coli (E. coli) shows that a higher initiation rate reduces the frequencies of FSE reformation, resulting in lower -1PRF efficiency. The role of translation initiation-mediated -1PRF was examined in an E. coli cellular copA/copA(Z) -1PRF event. The results showed that a higher translation initiation rate leads to lower -1PRF efficiency, sensitizing E. coli to copper stress. Together, these results suggest that translation initiation is an additional mechanism to regulate -1PRF to coordinate optimal protein synthesis for cell fitness, further providing the basis to investigate the interplay between translation initiation and elongation.