Yeast polypeptide chain release factors eRF1 and eRF3 are involved in cytoskeleton organization and cell cycle regulation

Abstract

Termination of translation in eukaryotes is controlled by two interacting polypeptide chain release factors, eRF1 and eRF3. eRF1 recognizes nonsense codons UAA, UAG, and UGA, while eRF3 stimulates polypeptide release from the ribosome in a GTP- and eRF1-dependent manner. In the yeast Saccharomyces cerevisiae, eRF1 and eRF3 are encoded by the SUP45 and SUP35 genes, respectively. Here we show that in yeast shortage of any one of the release factors was accompanied by a reduction in the levels of the other release factor and resulted in a substantial increase of nonsense codon readthrough. Besides, repression of the genes encoding these factors caused different effects on cell morphology. Repression of the SUP35 gene caused accumulation of cells of increased size with large buds. This was accompanied by the disappearance of actin cytoskeletal structures, impairment of the mitotic spindle structure, and defects in nuclei division and segregation in mitosis. The evolutionary conserved C-terminal domain of eRF3 similar to the elongation factor EF-1alpha was responsible for these effects. Repression of the SUP45 gene caused accumulation of unbudded cells with 2C and higher DNA content, indicating that DNA replication is uncoupled from budding. The data obtained suggest that eRF1 and eRF3 play additional, nontranslational roles in the yeast cell.

Mechanism of Cytoplasmic mRNA Translation

“…2) which functions with eIF6 in the dissociation of the ribosome into subunits for recycling (Pisarev et al, 2010). Yeast eRF1 has been shown to have additional functions that affect the cytoskeleton and cell cycle (Valouev et al, 2002) and appears to "moonlight" as observed for the eEFs (Le Sourd et al, 2006;Sasikumar et al, 2012) Arabidopsis has three AteRF1 genes that encode functional RFs (Chapman and Brown, 2004). The overexpression of AteRF1-1 resulted in the silencing of AteRF1-1 and to some extent AteRF1-2 and AteRF1-3 causing a phenotype known as broomhead (altered spacing between inflorescence stems cause a broom-like appearance) and is associated with perturbations in cell division and cell elongation (Petsch et al, 2005).…”

Eukaryotic release factors (eRFs) history

“…Repression of the SUP45 gene caused accumulation of unbudded cells with a higher DNA content. The depletion of eRF3 caused defects in action cytoskeleton, mitotic spindle, nuclei division and segregation (Valouev et al, 2002). It is well known that translation elongation factor EF-1A (EF-1a), which is highly homologous to the C-terminal 2/3 of Sup35 (eRF3), is involved in the control of microtubule dynamics in the cell cycle (Shiina et al, 1994) and can specifically interact either with aminoacyl-tRNAs or actin filaments in a pH-dependent manner .…”

Proteasomal degradation of human release factor eRF3a regulates translation termination complex formation

“…Depletion of eRF3a, which is likely to be the main factor acting in translation termination, causes a significant reduction of 1 the eRF1 level by decreasing its stability (Chauvin et al 2005). In budding yeast, some reports showed that a reduced level of either eRF1 or eRF3 did not affect the level of its partner (Chabelskaya et al 2004;Salas-Marco and Bedwell 2004), whereas Valouev et al (2002) reported that depletion of either of the release factors is accompanied by a reduction in the level of the other.…”