Toshifumi Inada

The potentially deleterious effects of aberrant mRNA lacking a termination codon (nonstop mRNA) are ameliorated by translation arrest, proteasome-mediated protein destabilization, and rapid mRNA degradation. Because polylysine synthesis via translation of the poly(A) mRNA tail leads to translation arrest and protein degradation by the proteasome, we examined the effects of other amino acid sequences. Insertion of 12 consecutive basic amino acids between GFP and HIS3 reporter genes, but not a ste

We conclude that the repression of beta-galactosidase expression by glucose is not due to the reduction of the cAMP-CRP level but due to an inducer exclusion mechanism which is mediated by the phosphoenolpyruvate-dependent sugar phosphotransferase system.

We describe a one-step affinity method for purifying ribosomes from the budding yeast Saccharomyces cerevisiae. Extracts from yeast strains expressing only C-terminally tagged Rpl25 protein or overexpressing this protein in the presence of endogenous Rpl25p were used as the starling materials. The purification was specific for tagged 60S subunits, and resulted in the copurification of 80S subunits and polysomes, as well as ribosome-associated proteins and mRNAs. Two of these associated proteins,

During protein synthesis, translating ribosomes encounter many challenges imposed by various types of defective mRNAs that can lead to reduced cellular fitness and, in some cases, even threaten cell viability. Aberrant translation leads to activation of one of several quality control pathways depending on the nature of the problem. These pathways promote the degradation of the problematic mRNA as well as the incomplete translation product, the nascent polypeptide chain. Many of these quality con

Accurate gene expression is a prerequisite for all cellular processes. Cells actively promote correct protein folding, which prevents the accumulation of abnormal and non-functional proteins. Translation elongation is the fundamental step in gene expression to ensure cellular functions, and abnormal translation arrest is recognized and removed by the quality controls. Recent studies demonstrated that ribosome plays crucial roles as a hub for gene regulation and quality controls. Ribosome-interac

18S non-functional rRNA decay (NRD) eliminates non-functional 18S rRNA with deleterious mutations in the decoding center. Dissociation of the non-functional 80S ribosome into 40S and 60S subunits is a prerequisite step for degradation of the non-functional 18S rRNA. However, the mechanisms by which the non-functional ribosome is recognized and dissociated into subunits remain elusive. Here, we report that the sequential ubiquitination of non-functional ribosomes is crucial for subunit dissociati

The era gene of Escherichia coli encodes a GTP-binding protein which has similarities to elongation factor Tu and the Saccharomyces cerevisiae RAS protein. To investigate its function, mutations affecting era were isolated. A mini-Tn10 insertion, which truncated 22 amino acids from the COOH end of Era, did not affect cell growth. By using this mini-Tn10 insert as a coselectable marker, a temperature-sensitive lethal era mutant was isolated by localized mutagenesis using P1 phage transduction. A

The lep gene of Escherichia coli encodes the leader peptidase which cleaves amino-terminal leader sequences of secreted proteins. To facilitate the study of structure-function relationships of the leader peptidase, 22 amber mutations in lep were isolated by localized mutagenesis. These amber mutants grew at 32 degrees C but not at 42 degrees C in the presence of a temperature-sensitive amber suppressor. Most of them were lethal under sup0 conditions. However, one amber mutant, the lep-9 mutant,

Ribosome-associated quality control (RQC) relieves stalled ribosomes and eliminates potentially toxic nascent polypeptide chains (NCs) that can cause neurodegeneration. During RQC, RQC2 modifies NCs with a C-terminal alanine and threonine (CAT) tail. CAT tailing promotes ubiquitination of NCs for proteasomal degradation, while RQC failure in budding yeast disrupts proteostasis via CAT-tailed NC aggregation. However, the CAT tail and its cytotoxicity in mammals have remained largely uncharacteriz