https://www.cell.com/molecular-cell/pdf/S1097-2765(03)00105-9.pdf

An Integrated Stress Response Regulates Amino Acid Metabolism and Resistance to Oxidative Stress

Regulation of Translation Initiation in Eukaryotes: Mechanisms and Biological Targets

Cells reprogram gene expression in response to environmental changes by mobilizing transcriptional activators. The activator protein Gcn4 of the yeast Saccharomyces cerevisiae is regulated by an intricate translational control mechanism, which is the primary focus of this review, and also by the modulation of its stability in response to nutrient availability. Translation of GCN4 mRNA is derepressed in amino acid-deprived cells, leading to transcriptional induction of nearly all genes encoding amino acid biosynthetic enzymes. The trans-acting proteins that control GCN4 translation have general functions in the initiation of protein synthesis, or regulate the activities of initiation factors, so that the molecular events that induce GCN4 translation also reduce the rate of general protein synthesis. This dual regulatory response enables cells to limit their consumption of amino acids while diverting resources into amino acid biosynthesis in nutrient-poor environments. Remarkably, mammalian cells use the same strategy to downregulate protein synthesis while inducing transcriptional activators of stress-response genes under various stressful conditions, including amino acid starvation.

Translational regulation of GCN4 and the general amino acid control of yeast.

Summary: ATP-binding cassette (ABC) systems are universally distributed among living organisms and function in many different aspects of bacterial physiology. ABC transporters are best known for their role in the import of essential nutrients and the export of toxic molecules, but they can also mediate the transport of many other physiological substrates. In a classical transport reaction, two highly conserved ATP-binding domains or subunits couple the binding/hydrolysis of ATP to the translocation of particular substrates across the membrane, through interactions with membrane-spanning domains of the transporter. Variations on this basic theme involve soluble ABC ATP-binding proteins that couple ATP hydrolysis to nontransport processes, such as DNA repair and gene expression regulation. Insights into the structure, function, and mechanism of action of bacterial ABC proteins are reported, based on phylogenetic comparisons as well as classic biochemical and genetic approaches. The availability of an increasing number of high-resolution structures has provided a valuable framework for interpretation of recent studies, and realistic models have been proposed to explain how these fascinating molecular machines use complex dynamic processes to fulfill their numerous biological functions. These advances are also important for elucidating the mechanism of action of eukaryotic ABC proteins, because functional defects in many of them are responsible for severe human inherited diseases.

Structure, Function, and Evolution of Bacterial ATP-Binding Cassette Systems

https://www.cell.com/immunity/pdf/S1074-7613(05)00108-1.pdf

GCN2 kinase in T cells mediates proliferative arrest and anergy induction in response to indoleamine 2,3-dioxygenase.

https://epublications.marquette.edu/cgi/viewcontent.cgi?article=1498&context=bio_fac

Uncharged tRNA activates GCN2 by displacing the protein kinase moiety from a bipartite tRNA-binding domain.

The Essential ATP-binding Cassette Protein RLI1 Functions in Translation by Promoting Preinitiation Complex Assembly

The essential vertebrate ABCE1 protein interacts with eukaryotic initiation factors.

Stimulation of GCN4 mRNA translation due to phosphorylation of the α-subunit of initiation factor 2 (eIF2) by its specific kinase, GCN2, requires binding of uncharged tRNA to a histidyl-tRNA synthetase (HisRS)-like domain in GCN2. GCN2 function in vivo also requires GCN1 and GCN20, but it was unknown whether these latter proteins act directly to promote the stimulation of GCN2 by uncharged tRNA. We found that the GCN1–GCN20 complex physically interacts with GCN2, binding to the N-terminus of the protein. Overexpression of N-terminal GCN2 segments had a dominant-negative phenotype that correlated with their ability to interact with GCN1–GCN20 and impede association between GCN1 and native GCN2. Consistently, this Gcn– phenotype was suppressed by overexpressing GCN2, GCN1–GCN20 or tRNAHis. The requirement for GCN1 was also reduced by overexpressing tRNAHis in a gcn1Δ strain. We conclude that binding of GCN1–GCN20 to GCN2 is required for its activation by uncharged tRNA. The homologous N-terminus of Drosophila GCN2 interacted with yeast GCN1–GCN20 and had a dominant Gcn– phenotype, suggesting evolutionary conservation of this interaction.

Association of GCN1–GCN20 regulatory complex with the N-terminus of eIF2α kinase GCN2 is required for GCN2 activation

GCN2 stimulates translation of GCN4 mRNA in amino acid-starved cells by phosphorylating translation initiation factor 2. GCN2 is activated by binding of uncharged tRNA to a domain related to histidyl-tRNA synthetase (HisRS). The HisRS-like region contains two dimerization domains (HisRS-N and HisRS-C) required for GCN2 function in vivo but dispensable for dimerization by full-length GCN2. Residues corresponding to amino acids at the dimer interface of Escherichia coli HisRS were required for dimerization of recombinant HisRS-N and for tRNA binding by full-length GCN2, suggesting that HisRS-N dimerization promotes tRNA binding and kinase activation. HisRS-N also interacted with the protein kinase (PK) domain, and a deletion impairing this interaction destroyed GCN2 function without reducing tRNA binding; thus, HisRS-N–PK interaction appears to stimulate PK function. The C-terminal domain of GCN2 (C-term) interacted with the PK domain in a manner disrupted by an activating PK mutation (E803V). These results suggest that the C-term is an autoinhibitory domain, counteracted by tRNA binding. We conclude that multiple domain interactions, positive and negative, mediate the activation of GCN2 by uncharged tRNA.

https://www.embopress.org/doi/pdf/10.1093/emboj/20.6.1425

The tRNA‐binding moiety in GCN2 contains a dimerization domain that interacts with the kinase domain and is required for tRNA binding and kinase activation

Jinsheng Dong

Papers

Uncharged tRNA activates GCN2 by displacing the protein kinase moiety from a bipartite tRNA-binding domain.

The Essential ATP-binding Cassette Protein RLI1 Functions in Translation by Promoting Preinitiation Complex Assembly

The essential vertebrate ABCE1 protein interacts with eukaryotic initiation factors.

Association of GCN1–GCN20 regulatory complex with the N-terminus of eIF2α kinase GCN2 is required for GCN2 activation

The tRNA‐binding moiety in GCN2 contains a dimerization domain that interacts with the kinase domain and is required for tRNA binding and kinase activation