RESUMO
Metabolic syndrome (MetS) is a term used to characterize individuals having at least three of the following diseases: obesity, dyslipidemia, hyperglycemia, insulin resistance, hypertension, and nonalcoholic fatty liver disease (NAFLD). It is widespread, and the number of individuals with MetS is increasing. However, the events leading to the manifestation of MetS are not well-understood. Here, we show that loss of murine ARV1 (mARV1) results in resistance to acquiring diseases associated with MetS. Arv1-/- animals fed a high-fat diet were resistant to diet-induced obesity, had lower blood cholesterol and triglyceride levels, and retained glucose tolerance and insulin sensitivity. Livers showed no gross morphological changes, contained lower levels of cholesterol, triglycerides, and fatty acids, and showed fewer signs of NAFLD. Knockout animals had elevated levels of liver farnesol X receptor (FXR) protein and its target, small heterodimer protein (SHP). They also had decreased levels of CYP7α1, CYP8ß1, and mature SREBP1 protein, evidence suggesting that liver FXR signaling was activated. Strengthening this hypothesis was the fact that peroxisome proliferator-activating receptor α (PPARα) protein was elevated, along with its target, fibroblast growth factor 21 (FGF21). Arv1-/- animals excreted more fecal cholesterol, free fatty acids, and bile acids. Their small intestines had 1) changes in bile acid composition, 2) an increase in the level of the intestinal FXR antagonist, tauromuricholic acid, and 3) showed signs of attenuated FXR signaling. Overall, we believe that ARV1 function is deleterious when consuming a high-fat diet. We further hypothesize that ARV1 is critical for initiating events required for the progression of diseases associated with MetS and NAFLD.
Assuntos
Proteínas de Transporte/genética , Deleção de Genes , Proteínas de Membrana/genética , Síndrome Metabólica/genética , Hepatopatia Gordurosa não Alcoólica/genética , Obesidade/genética , Animais , Colesterol/sangue , Dieta Hiperlipídica/efeitos adversos , Feminino , Resistência à Insulina , Fígado/metabolismo , Fígado/patologia , Masculino , Síndrome Metabólica/sangue , Síndrome Metabólica/patologia , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Hepatopatia Gordurosa não Alcoólica/sangue , Hepatopatia Gordurosa não Alcoólica/patologia , Obesidade/sangue , Obesidade/patologia , Triglicerídeos/sangueRESUMO
AMP kinase is a heterotrimeric serine/threonine protein kinase that regulates a number of metabolic processes, including lipid biosynthesis and metabolism. AMP kinase activity is regulated by phosphorylation, and the kinases involved have been uncovered. The particular phosphatases counteracting these kinases remain elusive. Here we discovered that the protein phosphatase 2A heterotrimer, PP2A(Ppp2r2d), regulates the phosphorylation state of AMP kinase by dephosphorylating Thr-172, a residue that activates kinase activity when phosphorylated. Co-immunoprecipitation and co-localization studies indicated that PP2A(Ppp2r2d) directly interacted with AMP kinase. PP2A(Ppp2r2d) dephosphorylated Thr-172 in rat aortic and human vascular smooth muscle cells. A positive correlation existed between decreased phosphorylation, decreased acetyl-CoA carboxylase Acc1 phosphorylation, and sterol response element-binding protein 1c-dependent gene expression. PP2A(Ppp2r2d) protein expression was up-regulated in the aortas of mice fed a high fat diet, and the increased expression correlated with increased blood lipid levels. Finally, we found that the aortas of mice fed a high fat diet had decreased AMP kinase Thr-172 phosphorylation, and contained an Ampk-PP2A(Ppp2r2d) complex. Thus, PP2A(Ppp2r2d) may antagonize the aortic AMP kinase activity necessary for maintaining normal aortic lipid metabolism. Inhibiting PP2A(Ppp2r2d) or activating AMP kinase represents a potential pharmacological treatment for many lipid-related diseases.
Assuntos
Proteínas Quinases Ativadas por AMP/antagonistas & inibidores , Proteína Fosfatase 2/química , Proteína Fosfatase 2/metabolismo , Quinases Proteína-Quinases Ativadas por AMP , Proteínas Quinases Ativadas por AMP/química , Animais , Aorta/metabolismo , Quinase da Proteína Quinase Dependente de Cálcio-Calmodulina/metabolismo , Linhagem Celular , Colesterol/metabolismo , Dieta Hiperlipídica/efeitos adversos , Inibidores Enzimáticos/farmacologia , Humanos , Metabolismo dos Lipídeos , Lipogênese , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Ácido Okadáico/farmacologia , Fosforilação , Proteína Fosfatase 2/antagonistas & inibidores , Proteínas Serina-Treonina Quinases/metabolismo , Estrutura Quaternária de Proteína , Subunidades Proteicas , RNA Interferente Pequeno/genética , Ratos , Proteína de Ligação a Elemento Regulador de Esterol 1/metabolismoRESUMO
Yeast two-hybrid (Y2H) studies have shown that cancerous Inhibitor of protein phosphatase 2A (CIP2A) interacted with several proteins, including leucine-rich repeat-containing protein 59 (LRRC59), suggesting that CIP2A may interact with the chromosome maintenance protein, shugoshin (Sgol1). We previously showed that LRRC59 interacted with CIP2A, which was required for CIP2A nuclear localization. Thus, we predicted that CIP2A and Sgol1 may also interact. Sgol1 is a nuclear protein that regulates chromosome segregation during cell division via protection of cohesin ring proteins. Here, we demonstrated that Sgol1 and the C-terminus of CIP2A interact in prostate carcinoma cell lines in a protein phosphatase 2A (PP2A)-dependent manner. Moreover, we demonstrated that depletion of CIP2A in PC-3 cells decreases premature chromosome segregation, whereas overexpression of CIP2A in an immortalized prostate cell line increases premature chromosome segregation. Importantly, we further showed that CIP2A depletion decreases the incidence of aneuploidy and stabilizes cohesin complex proteins, while overexpression of CIP2A destabilizes Sgol1. Thus, our findings strongly suggest that CIP2A promotes cell cycle progression, premature chromosome segregation, and aneuploidy, possibly through a novel interaction with Sgol1.
Assuntos
Autoantígenos/genética , Proteínas de Ciclo Celular/genética , Ciclo Celular/genética , Proteínas de Membrana/genética , Neoplasias da Próstata/genética , Aneuploidia , Apoptose/genética , Autoantígenos/biossíntese , Autoantígenos/metabolismo , Proteínas de Ciclo Celular/metabolismo , Linhagem Celular Tumoral , Segregação de Cromossomos/genética , Regulação Neoplásica da Expressão Gênica , Humanos , Peptídeos e Proteínas de Sinalização Intracelular , Masculino , Proteínas de Membrana/biossíntese , Proteínas de Membrana/metabolismo , Neoplasias da Próstata/patologia , Ligação ProteicaRESUMO
Using yeast two-hybrid analysis, we identified several novel protein interactions for the oncoprotein Cancerous Inhibitor of PP2A (CIP2A) and confirmed a subset of these interactions in human cancer cell lines. Analysis of the interaction in prostate carcinoma cells between CIP2A and leucine-rich repeat-containing protein 59 (LRRC59) suggests that CIP2A is translocated into the nucleus at G2/M through its association with LRRC59. Recent work by others has demonstrated that nuclear CIP2A disrupts mitotic checkpoints, which promotes deregulation of the cell cycle and increases cancerous phenotypes. Thus, we provide a novel therapeutic mechanism for inhibiting CIP2A function in cancerous cells via targeting the CIP2A-LRRC59 interaction.
Assuntos
Autoantígenos/metabolismo , Proteínas de Membrana/genética , Proteínas de Membrana/metabolismo , Neoplasias da Próstata/genética , Autoantígenos/biossíntese , Autoantígenos/genética , Ciclo Celular/genética , Linhagem Celular Tumoral , Regulação Neoplásica da Expressão Gênica , Humanos , Peptídeos e Proteínas de Sinalização Intracelular , Masculino , Proteínas de Membrana/biossíntese , Terapia de Alvo Molecular , Neoplasias da Próstata/tratamento farmacológico , Neoplasias da Próstata/patologia , Proteína Fosfatase 2/antagonistas & inibidores , Proteína Fosfatase 2/metabolismoRESUMO
Dysregulation of cholesterol homeostasis is associated with various metabolic diseases, including atherosclerosis and type 2 diabetes. The sterol response element binding protein (SREBP)-2 transcription factor induces the expression of genes involved in de novo cholesterol biosynthesis and low density lipoprotein (LDL) uptake, thus it plays a crucial role in maintaining cholesterol homeostasis. Here, we found that overexpressing microRNA (miR)-185 in HepG2 cells repressed SREBP-2 expression and protein level. miR-185-directed inhibition caused decreased SREBP-2-dependent gene expression, LDL uptake, and HMG-CoA reductase activity. In addition, we found that miR-185 expression was tightly regulated by SREBP-1c, through its binding to a single sterol response element in the miR-185 promoter. Moreover, we found that miR-185 expression levels were elevated in mice fed a high-fat diet, and this increase correlated with an increase in total cholesterol level and a decrease in SREBP-2 expression and protein. Finally, we found that individuals with high cholesterol had a 5-fold increase in serum miR-185 expression compared with control individuals. Thus, miR-185 controls cholesterol homeostasis through regulating SREBP-2 expression and activity. In turn, SREBP-1c regulates miR-185 expression through a complex cholesterol-responsive feedback loop. Thus, a novel axis regulating cholesterol homeostasis exists that exploits miR-185-dependent regulation of SREBP-2 and requires SREBP-1c for function.
Assuntos
Colesterol/biossíntese , Lipoproteínas LDL/metabolismo , MicroRNAs/genética , Regiões 3' não Traduzidas/genética , Animais , Linhagem Celular , Colesterol/sangue , Dieta Hiperlipídica/efeitos adversos , Regulação da Expressão Gênica/efeitos dos fármacos , Humanos , Hidroximetilglutaril-CoA Redutases/metabolismo , Insulina/farmacologia , Receptores X do Fígado , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Receptores Nucleares Órfãos/metabolismo , Transporte Proteico/efeitos dos fármacos , Receptores de LDL/metabolismo , Proteína de Ligação a Elemento Regulador de Esterol 1/metabolismo , Proteína de Ligação a Elemento Regulador de Esterol 2/genética , Transcrição Gênica/efeitos dos fármacosRESUMO
Saccharomyces cerevisiae ergosterol biosynthesis, like cholesterol biosynthesis in mammals, is regulated at the transcriptional level by a sterol feedback mechanism. Yeast studies defined a 7-bp consensus sterol-response element (SRE) common to genes involved in sterol biosynthesis and two transcription factors, Upc2 and Ecm22, which direct transcription of sterol biosynthetic genes. The 7-bp consensus SRE is identical to the anaerobic response element, AR1c. Data indicate that Upc2 and Ecm22 function through binding to this SRE site. We now show that it is two novel anaerobic AR1b elements in the UPC2 promoter that direct global ERG gene expression in response to a block in de novo ergosterol biosynthesis, brought about by antifungal drug treatment. The AR1b elements are absolutely required for auto-induction of UPC2 gene expression and protein and require Upc2 and Ecm22 for function. We further demonstrate the direct binding of recombinant expressed S. cerevisiae ScUpc2 and pathogenic Candida albicans CaUpc2 and Candida glabrata CgUpc2 to AR1b and SRE/AR1c elements. Recombinant endogenous promoter studies show that the UPC2 anaerobic AR1b elements act in trans to regulate ergosterol gene expression. Our results indicate that Upc2 must occupy UPC2 AR1b elements in order for ERG gene expression induction to take place. Thus, the two UPC2-AR1b elements drive expression of all ERG genes necessary for maintaining normal antifungal susceptibility, as wild type cells lacking these elements have increased susceptibility to azole antifungal drugs. Therefore, targeting these specific sites for antifungal therapy represents a novel approach to treat systemic fungal infections.
Assuntos
Genes Fúngicos , Elementos de Resposta , Esteróis/metabolismo , Aerobiose , Anaerobiose , Antifúngicos/farmacologia , Candida albicans/efeitos dos fármacos , Candida albicans/genética , Candida albicans/metabolismo , Candida glabrata/efeitos dos fármacos , Candida glabrata/genética , Candida glabrata/metabolismo , Ergosterol/genética , Regulação Fúngica da Expressão Gênica/efeitos dos fármacos , Lovastatina/farmacologia , Oxigenases de Função Mista/genética , Oxigenases de Função Mista/metabolismo , Regiões Promotoras Genéticas , Saccharomyces cerevisiae/efeitos dos fármacos , Saccharomyces cerevisiae/genética , Saccharomyces cerevisiae/metabolismo , Proteínas de Saccharomyces cerevisiae/genética , Proteínas de Saccharomyces cerevisiae/metabolismo , Transativadores/genética , Transativadores/metabolismoRESUMO
Infections by Candida albicans and related fungal pathogens pose a serious health problem for immunocompromised patients. Azole drugs, the most common agents used to combat infections, target the sterol biosynthetic pathway. Adaptation to azole therapy develops as drug-stressed cells compensate by upregulating several genes in the pathway, a process mediated in part by the Upc2 transcription factor. We have implemented a cell-based high-throughput screen to identify small-molecule inhibitors of Upc2-dependent induction of sterol gene expression in response to azole drug treatment. The assay is designed to identify not only Upc2 DNA binding inhibitors but also compounds impeding the activation of gene expression by Upc2. An AlphaScreen assay was developed to determine whether the compounds identified interact directly with Upc2 and inhibit DNA binding. Three compounds identified by the cell-based assay inhibited Upc2 protein level and UPC2-LacZ gene expression in response to a block in sterol biosynthesis. The compounds were growth inhibitory and attenuated antifungal-induced sterol gene expression in vivo. They did so by reducing the level of Upc2 protein and Upc2 DNA binding in the presence of drug. The mechanism by which the compounds restrict Upc2 DNA binding is not through a direct interaction, as demonstrated by a lack of DNA binding inhibitory activity using the AlphaScreen assay. Rather, they likely inhibit a novel pathway activating Upc2 in response to a block in sterol biosynthesis. We suggest that the compounds identified represent potential precursors for the synthesis of novel antifungal drugs.
Assuntos
Antifúngicos/farmacologia , Candida albicans/metabolismo , Proteínas Fúngicas/metabolismo , Fatores de Transcrição/metabolismo , Candida albicans/efeitos dos fármacos , Proteínas Fúngicas/genética , Regulação Fúngica da Expressão Gênica/efeitos dos fármacos , Regulação Fúngica da Expressão Gênica/genética , Transdução de Sinais/efeitos dos fármacos , Fatores de Transcrição/genéticaRESUMO
The lipid transporter Arv1 regulates sterol trafficking, and glycosylphosphatidylinositol and sphingolipid biosyntheses in Saccharomyces cerevisiae. ScArv1 contains an Arv1 homology domain (AHD) that is conserved at the amino acid level in the pathogenic fungal species, Candida albicans and Candida glabrata. Here we show S. cerevisiae cells lacking Arv1 are highly susceptible to antifungal drugs. In the presence of drug, Scarv1 cells are unable to induce ERG gene expression, have an altered pleiotrophic drug response, and are defective in multi-drug resistance efflux pump expression. All phenotypes are remediated by ectopic expression of CaARV1 or CgARV1. The AHDs of these pathogenic fungi are required for specific drug tolerance, demonstrating conservation of function. In order to understand how Arv1 regulates antifungal susceptibility, we examined sterol trafficking. CaARV1/CgARV1 expression suppressed the sterol trafficking defect of Scarv1 cells. Finally, we show that C. albicansarv1/arv1 cells are avirulent using a BALB/c disseminated mouse model. We suggest that overall cell survival in response to antifungal treatment requires the lipid transporter function of Arv1.
Assuntos
Candida albicans/genética , Candida albicans/patogenicidade , Proteínas de Membrana/genética , Proteínas de Saccharomyces cerevisiae/genética , Saccharomyces cerevisiae/genética , Esteróis/metabolismo , Animais , Antifúngicos , Resistência a Múltiplos Medicamentos/genética , Regulação Fúngica da Expressão Gênica , Metabolismo dos Lipídeos/genética , Camundongos , Transporte Proteico , Saccharomyces cerevisiae/metabolismo , Homologia de Sequência de AminoácidosRESUMO
Genome-wide association studies (GWAS) have linked IGF2BP2 single-nucleotide polymorphisms (SNPs) with type 2 diabetes (T2D). Mice overexpressing mIGF2BP2 have elevated cholesterol levels when fed a diet that induces hepatic steatosis. These and other studies suggest an important role for insulin growth factor 2 mRNA binding protein 2 (IGF2BP2) in the initiation and progression of several metabolic disorders. The ATPase binding cassette protein ABCA1 initiates nascent high-density apolipoprotein (HDL) biogenesis by transferring phospholipid and cholesterol to delipidated apolipoprotein AI (ApoAI). Individuals with mutational ablation of ABCA1 have Tangier disease, which is characterized by a complete loss of HDL. MicroRNA 33a and 33b (miR-33a/b) bind to the 3' untranslated region (UTR) of ABCA1 and repress its posttranscriptional gene expression. Here, we show that IGF2BP2 works together with miR-33a/b in repressing ABCA1 expression. Our data suggest that IGF2BP2 is an accessory protein of the argonaute (AGO2)-miR-33a/b-RISC complex, as it directly binds to miR-33a/b, AGO2, and the 3' UTR of ABCA1 Finally, we show that mice overexpressing human IGF2BP2 have decreased ABCA1 expression, increased low-density lipoprotein-cholesterol (LDL-C) and cholesterol blood levels, and elevated SREBP-dependent signaling. Our data support the hypothesis that IGF2BP2 has an important role in maintaining lipid homeostasis through its modulation of ABCA1 expression, as its overexpression or loss leads to dyslipidemia.
Assuntos
Transportador 1 de Cassete de Ligação de ATP/genética , Fator de Crescimento Insulin-Like II/genética , Fígado/metabolismo , MicroRNAs/genética , Animais , Colesterol/metabolismo , Diabetes Mellitus Tipo 2/genética , Regulação da Expressão Gênica/genética , Humanos , Insulina/metabolismo , Camundongos , Camundongos TransgênicosRESUMO
Ceramides and sphingolipid intermediates are well-established regulators of the cell cycle. In the budding yeast Saccharomyces cerevisae, the complex sphingolipid backbone, ceramide, comprises a long chain sphingoid base, a polar head group, and a very long chain fatty acid (VLCFA). While ceramides and long chain bases have been extensively studied as to their roles in regulating cell cycle arrest under multiple conditions, the roles of VLCFAs are not well understood. Here, we used the yeast elo2 and elo3 mutants, which are unable to elongate fatty acids, as tools to explore if maintaining VLCFA elongation is necessary for cell cycle arrest in response to yeast mating. We found that both elo2 and elo3 cells had severely reduced mating efficiencies and were unable to form polarized shmoo projections that are necessary for cell-cell contact during mating. They also lacked functional MAP kinase signaling activity and were defective in initiating a cell cycle arrest in response to pheromone. Additional data suggests that mislocalization of the Ste5 scaffold in elo2 and elo3 mutants upon mating initiation may be responsible for the inability to initiate a cell cycle arrest. Moreover, the lack of proper Ste5 localization may be caused by the inability of mutant cells to mobilize PIP2. We suggest that VLCFAs are required for Ste5 localization, which is a necessary event for initiating MAP kinase signaling and cell cycle arrest during yeast mating initiation.
Assuntos
Pontos de Checagem do Ciclo Celular/fisiologia , Ácidos Graxos/metabolismo , Ceramidas/metabolismo , Saccharomyces cerevisiae/metabolismo , Proteínas de Saccharomyces cerevisiae/metabolismo , Transdução de Sinais , Esfingolipídeos/metabolismoRESUMO
Sphingolipids are major constituents of membranes. A number of S. cerevisiae sphingolipid intermediates such as long chains sphingoid bases (LCBs) and ceramides act as signaling molecules regulating cell cycle progression, adaptability to heat stress, and survival in response to starvation. Here we show that S. cerevisiae haploid cells must synthesize ceramide in order to induce mating specific cell cycle arrest. Cells devoid of sphingolipid biosynthesis or defective in ceramide synthesis are sterile and harbor defects in pheromone-induced MAP kinase-dependent transcription. Analyses of G1/S cyclin levels indicate that mutant cells cannot reduce Cln1/2 levels in response to pheromone. FACS analysis indicates a lack of ability to arrest. The addition of LCBs to sphingolipid deficient cells restores MAP kinase-dependent transcription, reduces cyclin levels, and allows for mating, as does the addition of a cell permeable ceramide to cells blocked at ceramide synthesis. Pharmacological studies using the inositolphosphorylceramide synthase inhibitor aureobasidin A indicate that the ability to synthesize and accumulate ceramide alone is sufficient for cell cycle arrest and mating. Studies indicate that ceramide also has a role in PI(4,5)P2 polarization during mating, an event necessary for initiating cell cycle arrest and mating itself. Moreover, our studies suggest a third role for ceramide in localizing the mating-specific Ste5 scaffold to the plasma membrane. Thus, ceramide plays a role 1) in pheromone-induced cell cycle arrest, 2) in activation of MAP kinase-dependent transcription, and 3) in PtdIns(4,5)P2 polarization. All three events are required for differentiation during yeast mating.
Assuntos
Ceramidas/metabolismo , Proteínas de Saccharomyces cerevisiae/metabolismo , Saccharomyces cerevisiae/metabolismo , Ceramidase Alcalina , Amidoidrolases/metabolismo , Pontos de Checagem do Ciclo Celular/efeitos dos fármacos , Membrana Celular/metabolismo , Ciclinas/metabolismo , Immunoblotting , Microscopia de Fluorescência , Proteínas Quinases Ativadas por Mitógeno/metabolismo , Oxirredutases/genética , Oxirredutases/metabolismo , Feromônios/farmacologia , Proteínas de Saccharomyces cerevisiae/genética , Transdução de Sinais , Esfingolipídeos/biossíntese , Fatores de Transcrição/metabolismoRESUMO
Candida albicans is an opportunistic fungus responsible for the majority of systemic fungal infections. Multiple factors contribute to C. albicans pathogenicity. C. albicans strains lacking CaArv1 are avirulent. Arv1 has a conserved Arv1 homology domain (AHD) that has a zinc-binding domain containing two cysteine clusters. Here, we explored the role of the CaAHD and zinc-binding motif in CaArv1-dependent virulence. Overall, we found that the CaAHD was necessary but not sufficient for cells to be virulent, whereas the zinc-binding domain was essential, as Caarv1/Caarv1 cells expressing the full-length zinc-binding domain mutants, Caarv1C3S and Caarv1C28S, were avirulent. Phenotypically, we found a direct correlation between the avirulence of Caarv1/Caarv1, Caarrv1AHD , Caarv1C3S , and Caarv1C28S cells and defects in bud site selection, septa formation and localization, and hyphal formation and elongation. Importantly, all avirulent mutant strains lacked the ability to maintain proper sterol distribution. Overall, our results have established the importance of the AHD and zinc-binding domain in fungal invasion, and have correlated an avirulent phenotype with the inability to maintain proper sterol distribution.
RESUMO
Maintaining accurate progression through the cell cycle requires the proper temporal expression and regulation of cyclins. The mammalian D-type cyclins promote G1-S transition. D1 cyclin protein stability is regulated through its ubiquitylation and resulting proteolysis catalyzed by the SCF E3 ubiquitin ligase complex containing the F-box protein, Fbx4. SCF E3-ligase-dependent ubiquitylation of D1 is trigged by an increase in the phosphorylation status of the cyclin. As inhibition of ubiquitin-dependent D1 degradation is seen in many human cancers, we set out to uncover how D-type cyclin phosphorylation is regulated. Here we show that in S. cerevisiae, a heterotrimeric protein phosphatase 2A (PP2A(Cdc55)) containing the mammalian PPP2R2/PR55 B subunit ortholog Cdc55 regulates the stability of the G1 cyclin Cln2 by directly regulating its phosphorylation state. Cells lacking Cdc55 contain drastically reduced Cln2 levels caused by degradation due to cdk-dependent hyperphosphorylation, as a Cln2 mutant unable to be phosphorylated by the yeast cdk Cdc28 is highly stable in cdc55-null cells. Moreover, cdc55-null cells become inviable when the SCF(Grr1) activity known to regulate Cln2 levels is eliminated or when Cln2 is overexpressed, indicating a critical relationship between SCF and PP2A functions in regulating cell cycle progression through modulation of G1-S cyclin degradation/stability. In sum, our results indicate that PP2A is absolutely required to maintain G1-S cyclin levels through modulating their phosphorylation status, an event necessary to properly transit through the cell cycle.
Assuntos
Proteínas de Ciclo Celular/metabolismo , Ciclo Celular/fisiologia , Ciclina G1/metabolismo , Ciclinas/metabolismo , Proteína Fosfatase 2/metabolismo , Proteínas de Saccharomyces cerevisiae/metabolismo , Saccharomyces cerevisiae/fisiologia , Western Blotting , Imunoprecipitação , Mutagênese , Fosforilação , Estabilidade Proteica , Saccharomyces cerevisiae/metabolismo , Tripeptidil-Peptidase 1RESUMO
Protein phosphatase 2A (PP2A) is a heterotrimer consisting of A and B regulatory subunits and a C catalytic subunit. PP2A regulates mitotic cell events that include the cell cycle, nutrient sensing, p53 stability and various mitogenic signals. The role of PP2A during meiosis is less understood. We explored the role of Saccharomyces cerevisiae PP2A during meiosis. We show a PP2A (Cdc)55 containing the human B/55 family B subunit ortholog, Cdc55, is required for progression through meiosis I. Mutant cells lacking Cdc55 remain mononucleated. They harbor meiotic gene expression, premeiotic DNA replication, homologous recombination and spindle pole body (SPB) defects. They initiate but do not complete replication and are defective in performing intergenic homologous recombination. Bypass alleles, which allow cells defective in recombination to finish meiosis, do not suppress the meiosis I defect. cdc55 cells arrest with a single SPB lacking microtubules, or duplicated but not separated SBPs containing microtubules. Finally, the premeiotic replication defect is suppressed by loss of Rad9 checkpoint function. We conclude PP2A (Cdc)55 is required for the proper temporal initiation of multiple meiotic events and/or monitors these events to ensure their fidelity.