RESUMO
The ataxia-telangiectasia mutated/ATM and Rad3-related (ATM/ATR) family proteins are evolutionarily conserved serine/threonine kinases best known for their roles in mediating the DNA damage response. Upon activation, ATM/ATR phosphorylate numerous targets to stabilize stalled replication forks, repair damaged DNA, and inhibit cell cycle progression to ensure survival of the cell and safeguard integrity of the genome. Intriguingly, separation of function alleles of the human ATM and MEC1, the budding yeast ATM/ATR, were shown to confer widespread protein aggregation and acute sensitivity to different types of proteotoxic agents including heavy metal, amino acid analogue, and an aggregation-prone peptide derived from the Huntington's disease protein. Further analyses unveiled that ATM and Mec1 promote resistance to perturbation in protein homeostasis via a mechanism distinct from the DNA damage response. In this minireview, we summarize the key findings and discuss ATM/ATR as a multifaceted signalling protein capable of mediating cellular response to both DNA and protein damage.
Assuntos
Proteínas Mutadas de Ataxia Telangiectasia/metabolismo , Dano ao DNA , Reparo do DNA , Replicação do DNA , Estresse Oxidativo , Proteostase , Proteínas Mutadas de Ataxia Telangiectasia/genética , Humanos , Transdução de SinaisRESUMO
Unlike most checkpoint proteins, Mec1, an ATM/ATR kinase, is essential. We utilized mec1-4, a missense allele (E2130K) that confers diminished kinase activity, to interrogate the question. Unbiased screen for genetic interactors of mec1-4 identified numerous genes involved in proteostasis. mec1-4 confers sensitivity to heat, an amino acid analog, and Htt103Q, an aggregation-prone model peptide of Huntingtin. Oppositely, mec1-4 confers resistance to cycloheximide, a translation inhibitor. In response to heat, mec1-4 leads to widespread protein aggregation and cell death. Key components of the Mec1 signaling network, Rad53CHK1, Dun1, and Sml1, also impact survival in response to proteotoxic stress. Activation of autophagy or sml1Δ promotes aggregate resolution and rescues mec1-4 lethality. These findings show that proteostasis is a fundamental function of Mec1 and that Mec1 is likely to utilize its checkpoint response network to mediate resistance to proteotoxic stress, a role that may be conserved from yeast to mammalian cells.
Assuntos
Proteínas de Ciclo Celular/metabolismo , Peptídeos e Proteínas de Sinalização Intracelular/metabolismo , Proteínas Serina-Treonina Quinases/metabolismo , Proteostase/fisiologia , Proteínas de Saccharomyces cerevisiae/metabolismo , Quinase do Ponto de Checagem 2/metabolismo , Dano ao DNA/fisiologia , Peptídeos e Proteínas de Sinalização Intracelular/genética , Fosforilação , Proteínas Serina-Treonina Quinases/genética , Saccharomyces cerevisiae , Proteínas de Saccharomyces cerevisiae/genética , SaccharomycetalesRESUMO
Copper is an essential but potentially toxic redox-active metal, so the levels and distribution of this metal are carefully regulated to ensure that it binds to the correct proteins. Previous studies of copper-dependent transcription in the yeast Saccharomyces cerevisiae have focused on the response of genes to changes in the exogenous levels of copper. We now report that yeast copper genes are regulated in response to the DNA-damaging agents methyl methanesulfonate (MMS) and hydroxyurea by a mechanism(s) that requires the copper-responsive transcription factors Mac1 and AceI, copper superoxide dismutase (Sod1) activity, and the Rad53 checkpoint kinase. Furthermore, in copper-starved yeast, the response of the Rad53 pathway to MMS is compromised due to a loss of Sod1 activity, consistent with the model that yeast imports copper to ensure Sod1 activity and Rad53 signaling. Crucially, the Mac1 transcription factor undergoes changes in its redox state in response to changing levels of copper or MMS. This study has therefore identified a novel regulatory relationship between cellular redox, copper homeostasis, and the DNA damage response in yeast.
Assuntos
Cobre/metabolismo , Dano ao DNA , DNA Fúngico/metabolismo , Regulação Fúngica da Expressão Gênica/efeitos dos fármacos , Saccharomyces cerevisiae/metabolismo , Proteínas de Ciclo Celular/genética , Proteínas de Ciclo Celular/metabolismo , Quinase do Ponto de Checagem 2/genética , Quinase do Ponto de Checagem 2/metabolismo , Cobre/farmacologia , DNA Fúngico/genética , Proteínas de Ligação a DNA/genética , Proteínas de Ligação a DNA/metabolismo , Hidroxiureia/farmacologia , Metanossulfonato de Metila/farmacologia , Proteínas Nucleares/genética , Proteínas Nucleares/metabolismo , Oxirredução , Saccharomyces cerevisiae/efeitos dos fármacos , Saccharomyces cerevisiae/genética , Proteínas de Saccharomyces cerevisiae/genética , Proteínas de Saccharomyces cerevisiae/metabolismo , Transdução de Sinais , Superóxido Dismutase/genética , Superóxido Dismutase/metabolismo , Superóxido Dismutase-1 , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismoRESUMO
PtdIns(3,5)P(2) is one of the seven regulatory PPIn (polyphosphoinositides) that are ubiquitous in eukaryotes. It controls membrane trafficking at multiple points in the endosomal/lysosomal system and consequently regulates the size, shape and acidity of at least one endo-lysosomal compartment. PtdIns(3,5)P(2) appears to exert this control via multiple effector proteins, with each effector specific for a subset of the various PtdIns(3,5)P(2)-dependent processes. Some putative PtdIns(3,5)P(2) effectors have been identified, including Atg18p-related PROPPIN [beta-propeller(s) that bind PPIn] proteins and the epsin-like proteins Ent3p and Ent5p, whereas others remain to be defined. One of the principal functions of PtdIns(3,5)P(2) is to regulate the fission/fragmentation of endo-lysosomal sub-compartments. PtdIns(3,5)P(2) is required for vesicle formation during protein trafficking between endo-lysosomes and also for fragmentation of endo-lysosomes into smaller compartments. In yeast, hyperosmotic stress accelerates the latter process. In the present review we highlight and discuss recent studies that reveal the role of the HOPS-CORVET complex and the vacuolar H(+)-ATPase in the process of endo-lysosome fission, and speculate on connections between these machineries and the Fab1p pathway. We also discuss new evidence linking PtdIns(3,5)P(2) and PtdIns5P to the regulation of exocytosis.
