Termination of translation in eukaryotes

1995 ◽  
Vol 73 (11-12) ◽  
pp. 1079-1086 ◽  
Author(s):  
Lev L. Kisselev ◽  
Lyudmila Yu. Frolova
Keyword(s):  
Polypeptide Chain ◽  
Translation Termination ◽  
Protein Biosynthesis ◽  
High Rate ◽  
Vitro Assay ◽  
Binding Motifs ◽  
Stop Codons ◽  
Release Factors ◽  
Terminal Domain ◽  
Gtp Binding

Termination of translation is governed in ribosomes by polypeptide chain release factors (pRF and eRF in prokaryotes and eukaryotes, respectively). In prokaryotes, three pRF have been identified and sequenced, while in eukaryotes, only a single eRF has been identified to date. Recently, we have characterized a highly conserved protein family called eRF1. At least, human and Xenopus laevis proteins from this family are active as eRFs in the in vitro assay with any of the three stop codons. No structural similarity has been revealed between any of the three pRFs and eRF1 family. Furthermore, GTP-binding motifs have not been revealed, although translation termination in eukaryotes is a GTP-dependent process. We have demonstrated that in eukaryotes a second eRF exists in addition to eRF1, called eRF3. The eRF3 family has two features in common: presence of GTP-binding motifs and high conservation of the C-terminal domain structure. The C-terminal domain of the X. laevis eRF3 has no RF activity although it stimulates the eRF1 activity considerably at low concentration of the stop codons, conferring GTP dependence to the termination reaction. Without eRF3, the eRF1 activity is entirely GTP independent. Some features of X. laevis eRF3 (C-terminal domain) resemble those of pRF3. The newly identified eRF1 and eRF3 are structurally conserved and distinct from the respective pRF1/2 and pRF3 proteins, pointing to the possibility of different evolution of translation termination machinery in prokaryotes and eukaryotes. Bipartition of the translation termination apparatus probably provides high rate and accuracy of translation termination.Key words: higher eukaryotic polypeptide chain release factors, translation termination, protein biosynthesis.

scholarly journals Interaction between yeast Sup45p (eRF1) and Sup35p (eRF3) polypeptide chain release factors: implications for prion-dependent regulation.

1997 ◽  
Vol 17 (5) ◽  
pp. 2798-2805 ◽  
Author(s):  
S V Paushkin ◽  
V V Kushnirov ◽  
V N Smirnov ◽  
M D Ter-Avanesyan
Keyword(s):  
Polypeptide Chain ◽  
Translation Termination ◽  
Regulation Of Gene Expression ◽  
Release Factor ◽  
Middle Region ◽  
Conformational Switch ◽  
Release Factors ◽  
Terminal Domain ◽  
Nonsense Suppressor ◽  
Mammalian Prions

The SUP45 and SUP35 genes of Saccharomyces cerevisiae encode polypeptide chain release factors eRF1 and eRF3, respectively. It has been suggested that the Sup35 protein (Sup35p) is subject to a heritable conformational switch, similar to mammalian prions, thus giving rise to the non-Mendelian [PSI+] nonsense suppressor determinant. In a [PSI+] state, Sup35p forms high-molecular-weight aggregates which may inhibit Sup35p activity, leading to the [PSI+] phenotype. Sup35p is composed of the N-terminal domain (N) required for [PSI+] maintenance, the presumably nonfunctional middle region (M), and the C-terminal domain (C) essential for translation termination. In this study, we observed that the N domain, alone or as a part of larger fragments, can form aggregates in [PSI+] cells. Two sites for Sup45p binding were found within Sup35p: one is formed by the N and M domains, and the other is located within the C domain. Similarly to Sup35p, in [PSI+] cells Sup45p was found in aggregates. The aggregation of Sup45p is caused by its binding to Sup35p and was not observed when the aggregated Sup35p fragments did not contain sites for Sup45p binding. The incorporation of Sup45p into the aggregates should inhibit its activity. The N domain of Sup35p, responsible for its aggregation in [PSI+] cells, may thus act as a repressor of another polypeptide chain release factor, Sup45p. This phenomenon represents a novel mechanism of regulation of gene expression at the posttranslational level.

scholarly journals Mechanisms that ensure speed and fidelity in eukaryotic translation termination

2021 ◽  
Author(s):  
Michael R Lawson ◽  
Laura N Lessen ◽  
Jinfan Wang ◽  
Arjun Prabhakar ◽  
Nicholas C Corsepius ◽  
...  
Keyword(s):  
Single Molecule ◽  
Translation Termination ◽  
Translation System ◽  
Single Molecule Fluorescence ◽  
Translation Elongation ◽  
Eukaryotic Translation ◽  
Stop Codons ◽  
Release Factors ◽  
Molecular Events

Translation termination, which liberates a nascent polypeptide from the ribosome specifically at stop codons, must occur accurately and rapidly. We established single molecule fluorescence assays to track the dynamics of ribosomes and two requisite release factors (eRF1 and eRF3) throughout termination using an in vitro reconstituted yeast translation system. We found that the two eukaryotic release factors bind together to recognize stop codons rapidly and elicit termination via a tightly regulated, multi-step process that resembles tRNA selection during translation elongation. Because the release factors are conserved from yeast to humans, the molecular events that underlie yeast translation termination are likely broadly fundamental to eukaryotic protein synthesis.

scholarly journals Iron in Translation: From the Beginning to the End

2021 ◽  
Vol 9 (5) ◽  
pp. 1058
Author(s):  
Antonia María Romero ◽  
María Teresa Martínez-Pastor ◽  
Sergi Puig
Keyword(s):  
Translational Regulation ◽  
Translation Termination ◽  
Protein Biosynthesis ◽  
Regulatory Protein ◽  
Dynamic Control ◽  
Essential Element ◽  
Cellular Functions ◽  
Yeast Saccharomyces Cerevisiae ◽  
Eukaryotic Translation ◽  
Responsive Element

Iron is an essential element for all eukaryotes, since it acts as a cofactor for many enzymes involved in basic cellular functions, including translation. While the mammalian iron-regulatory protein/iron-responsive element (IRP/IRE) system arose as one of the first examples of translational regulation in higher eukaryotes, little is known about the contribution of iron itself to the different stages of eukaryotic translation. In the yeast Saccharomyces cerevisiae, iron deficiency provokes a global impairment of translation at the initiation step, which is mediated by the Gcn2-eIF2α pathway, while the post-transcriptional regulator Cth2 specifically represses the translation of a subgroup of iron-related transcripts. In addition, several steps of the translation process depend on iron-containing enzymes, including particular modifications of translation elongation factors and transfer RNAs (tRNAs), and translation termination by the ATP-binding cassette family member Rli1 (ABCE1 in humans) and the prolyl hydroxylase Tpa1. The influence of these modifications and their correlation with codon bias in the dynamic control of protein biosynthesis, mainly in response to stress, is emerging as an interesting focus of research. Taking S. cerevisiae as a model, we hereby discuss the relevance of iron in the control of global and specific translation steps.

scholarly journals p190 RhoGAP, the major RasGAP-associated protein, binds GTP directly.

1994 ◽  
Vol 14 (11) ◽  
pp. 7173-7181 ◽  
Author(s):  
R Foster ◽  
K Q Hu ◽  
D A Shaywitz ◽  
J Settleman
Keyword(s):  
Structural Features ◽  
Cellular Protein ◽  
Small Gtpases ◽  
Sequence Motifs ◽  
Amino Terminal ◽  
Terminal Domain ◽  
Gtp Binding ◽  
Guanine Nucleotide Binding ◽  
Complex Forms ◽  
Carboxy Terminal

In mitogenically stimulated cells, a specific complex forms between the Ras GTPase-activating protein (RasGAP) and the cellular protein p190. We have previously reported that p190 contains a carboxy-terminal domain that functions as a GAP for the Rho family GTPases. Thus, the RasGAP-p190 complex may serve to couple Ras- and Rho-mediated signalling pathways. In addition to its RhoGAP domain, p190 contains an amino-terminal domain that contains sequence motifs found in all known GTPases. Here, we report that p190 binds GTP and GDP through this conserved domain and that the structural requirements for binding are similar to those seen with other GTPases. While the purified protein is unable to hydrolyze GTP, we detect an activity in cell lysates that can promote GTP hydrolysis by p190. A mutated form of p190 that fails to bind nucleotide retains its RasGAP binding and RhoGAP activities, indicating that GTP binding by p190 is not required for these functions. The sequence of p190 in the GTP-binding domain, which shares structural features with both the Ras-like small GTPases and the larger G proteins, suggests that this protein defines a novel class of guanine nucleotide-binding proteins.

scholarly journals GSP1 and GSP2, genetic suppressors of the prp20-1 mutant in Saccharomyces cerevisiae: GTP-binding proteins involved in the maintenance of nuclear organization.

1993 ◽  
Vol 13 (4) ◽  
pp. 2152-2161 ◽  
Author(s):  
P Belhumeur ◽  
A Lee ◽  
R Tam ◽  
T DiPaolo ◽  
N Fortin ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Dna Replication ◽  
Essential Gene ◽  
Negative Control ◽  
Temperature Sensitive ◽  
Vitro Assay ◽  
Gtp Binding ◽  
Genetic Suppressors ◽  
Multicopy Suppressors

The temperature-sensitive mutation prp20-1 of Saccharomyces cerevisiae exhibits a pleiotropic phenotype associated with a general failure to maintain a proper organization of the nucleus. Its mammalian homolog, RCC1, is not only reported to be involved in the negative control of chromosome condensation but is also believed to assist in the coupling of DNA replication to the entry into mitosis. Recent studies on Xenopus RCC1 have strongly suggested a further role for this protein in the formation or maintenance of the DNA replication machinery. To elucidate the nature of the various components required for this PRP20 control pathway in S. cerevisiae, we undertook a search for multicopy suppressors of a prp20 thermosensitive mutant. Two genes, GSP1 and GSP2, were identified that encode almost identical polypeptides of 219 and 220 amino acids. Sequence analyses of these proteins show them to contain the ras consensus domains involved in GTP binding and metabolism. The levels of the GSP1 transcript are about 10-fold those of GSP2. As for S. cerevisiae RAS2, GSP2 expression exhibits carbon source dependency, while GSP1 expression does not. GSP1 is an essential gene, and GSP2 is not required for cell viability. We show that GSP1p is nuclear, that it can bind GTP in an in vitro assay, and finally, that a mutation in GSP1p which activates small ras-like proteins by increasing the stability of the GTP-bound form causes a dominant lethal phenotype. We believe that these two gene products may serve in regulating the activities of the multicomponent PRP20 complex.

scholarly journals The Eukaryotic Polypeptide Chain Releasing Factor (eRF3/GSPT) Carrying the Translation Termination Signal to the 3′-Poly(A) Tail of mRNA

1999 ◽  
Vol 274 (24) ◽  
pp. 16677-16680 ◽  
Author(s):  
Shin-ichi Hoshino ◽  
Mariko Imai ◽  
Tetsuo Kobayashi ◽  
Naoyuki Uchida ◽  
Toshiaki Katada
Keyword(s):  
Polypeptide Chain ◽  
Translation Termination
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