RESUMO
Polo like kinase 4 (Plk4) is a tightly regulated serine threonine kinase that governs centriole duplication. Increased Plk4 expression, which is a feature of many common human cancers, causes centriole overduplication, mitotic irregularities, and chromosomal instability. Plk4 can also promote cancer invasion and metastasis through regulation of the actin cytoskeleton. Herein we demonstrate physical interaction of Plk4 with FAM46C/TENT5C, a conserved protein of unknown function until recently. FAM46C localizes to centrioles, inhibits Plk4 kinase activity, and suppresses Plk4-induced centriole duplication. Interference with Plk4 function by FAM46C was independent of the latter's nucleotidyl transferase activity. In addition, FAM46C restrained cancer cell invasion and suppressed MDA MB-435 cancer growth in a xenograft model, opposing the effect of Plk4. We demonstrate loss of FAM46C in patient-derived colorectal cancer tumor tissue that becomes more profound with advanced clinical stage. These results implicate FAM46C as a tumor suppressor that acts by inhibiting Plk4 activity.
Assuntos
Genes Supressores de Tumor , Nucleotidiltransferases/metabolismo , Animais , Linhagem Celular Tumoral , Centríolos/metabolismo , Neoplasias Colorretais/patologia , Sequência Conservada , Humanos , Camundongos Nus , Fosforilação , Ligação Proteica , Domínios Proteicos , Proteínas Serina-Treonina Quinases/química , Proteínas Serina-Treonina Quinases/metabolismo , Ensaios Antitumorais Modelo de XenoenxertoRESUMO
The African Pharmacogenomics Consortium (APC) was formally launched on the 6th September 2018. This white paper outlines its vision, and objectives towards addressing challenges of conducting and applying pharmacogenomics in Africa and identifies opportunities for advancement of individualized drugs use on the continent. Africa, especially south of the Sahara, is beset with a huge burden of infectious diseases with much co-morbidity whose multiplicity and intersection are major challenges in achieving the sustainable development goals (SDG), SDG3, on health and wellness. The profile of drugs commonly used in African populations lead to a different spectrum of adverse drug reactions (ADRs) when compared to other parts of the world. Coupled with the genetic diversity among Africans, the APC is established to promote pharmacogenomics research and its clinical implementation for safe and effective use of medicine in the continent. Variation in the way patients respond to treatment is mainly due to differences in activity of enzymes and transporters involved in pathways associated with each drug's disposition. Knowledge of pharmacogenomics, therefore, helps in identifying genetic variants in these proteins and their functional effects. Africa needs to consolidate its pharmacogenomics expertise and technological platforms to bring pharmacogenomics to use.
RESUMO
Aneuploidy is a characteristic feature of established cancers and can promote tumor development. Aneuploidy may arise directly, through unequal distribution of chromosomes into daughter cells, or indirectly, through a tetraploid intermediate. The polo family kinase Plk4/Sak is required for late mitotic progression and is haploinsufficient for tumor suppression in mice. Here we show that loss of heterozygosity (LOH) occurs at the Plk4 locus in 50% of human hepatocellular carcinomas (HCC) and is present even in preneoplastic cirrhotic liver nodules. LOH at Plk4 is associated with reduced Plk4 expression in HCC tumors but not with mutations in the remaining allele. Plk4(+/-) murine embryonic fibroblasts (MEFs) at early passage show a high incidence of multinucleation, supernumerary centrosomes, and a near-tetraploid karyotype. Underlying these phenotypes is a high rate of primary cytokinesis failure, associated with aberrant actomyosin ring formation, reduced RhoA activation, and failure to localize the RhoA guanine nucleotide exchange factor Ect2 to the spindle midbody. We further show that Plk4 normally localizes to the midbody and binds to and phosphorylates Ect2 in vitro. With serial passaging Plk4(+/-) MEFs rapidly immortalize, acquiring an increasing burden of nonclonal and clonal gross chromosomal irregularities, and form tumors in vivo. Our results indicate that haploid levels of Plk4 disrupt RhoGTPase function during cytokinesis, resulting in aneuploidy and tumorigenesis, thus implicating early LOH at Plk4 as one of the drivers of human hepatocellular carcinogenesis. These findings represent an advance in our understanding of genetic predisposition to HCC, which continues to increase in incidence globally and particularly in North America.
Assuntos
Instabilidade Cromossômica , Regulação da Expressão Gênica , Proteínas Serina-Treonina Quinases/metabolismo , Alelos , Animais , Linhagem Celular Tumoral , Citocinese , Fibroblastos/metabolismo , Humanos , Camundongos , Camundongos SCID , Mitose , Modelos Biológicos , Fosforilação , Proteínas Serina-Treonina Quinases/fisiologiaRESUMO
Kae1 is a universally conserved ATPase and part of the essential gene set in bacteria. In archaea and eukaryotes, Kae1 is embedded within the protein kinase-containing KEOPS complex. Mutation of KEOPS subunits in yeast leads to striking telomere and transcription defects, but the exact biochemical function of KEOPS is not known. As a first step to elucidating its function, we solved the atomic structure of archaea-derived KEOPS complexes involving Kae1, Bud32, Pcc1, and Cgi121 subunits. Our studies suggest that Kae1 is regulated at two levels by the primordial protein kinase Bud32, which is itself regulated by Cgi121. Moreover, Pcc1 appears to function as a dimerization module, perhaps suggesting that KEOPS may be a processive molecular machine. Lastly, as Bud32 lacks the conventional substrate-recognition infrastructure of eukaryotic protein kinases including an activation segment, Bud32 may provide a glimpse of the evolutionary history of the protein kinase family.
Assuntos
Proteínas Arqueais/química , Complexos Multiproteicos/química , Proteínas Quinases/química , Proteínas Arqueais/genética , Proteínas Arqueais/metabolismo , Proteínas de Transporte/química , Cristalografia por Raios X , Escherichia coli/genética , Humanos , Peptídeos e Proteínas de Sinalização Intracelular , Mathanococcus/genética , Mathanococcus/metabolismo , Modelos Moleculares , Complexos Multiproteicos/fisiologia , Ressonância Magnética Nuclear Biomolecular , Proteínas Quinases/genética , Proteínas Quinases/metabolismo , Estrutura Terciária de Proteína , Subunidades Proteicas/química , Homologia de Sequência de Aminoácidos , Telômero/metabolismo , Thermoplasma/genética , Thermoplasma/metabolismo , Transcrição GênicaRESUMO
The proline-rich, extensin-like receptor kinase (PERK) family is characterized by a putative extracellular domain related to cell wall proteins, followed by a transmembrane domain and kinase domain. The original member, PERK1, was isolated from Brassica napus (BnPERK1) and 15 PERK1-related members were subsequently identified in the Arabidopsis thaliana genome. Ectopic expression and antisense suppression studies were performed using the BnPERK1 cDNA under the control of the 35S CaMV constitutive promoter and introduced into Arabidopsis. In the case of antisense suppression, the BnPERK1 cDNA shared sufficient sequence similarity to suppress several members of the At PERK family. In both sets of transgenic Arabidopsis, several heritable changes in growth and development were observed. Antisense BnPERK1 transgenic Arabidopsis showed various growth defects including loss of apical dominance, increased secondary branching, and floral organ defects. In contrast, Arabidopsis plants ectopically expressing BnPERK1 displayed a prolonged lifespan with increased lateral shoot production and seed set. Along with these phenotypic changes, aberrant deposits of callose and cellulose were also observed, suggestive of cell wall changes as a consequence of altered PERK expression.
RESUMO
In Brassica , the thioredoxin h proteins, THL1 and THL2, were previously found to be potential inhibitors of the S receptor kinase (SRK) in the Brassica self-incompatibility response. To investigate the biological roles of THL1 and THL2 in pollen-pistil interactions, the stigma-specific SLR1 promoter was used to drive antisense THL1/2 expression in Brassica napus cv. Westar. This cultivar is normally compatible, but antisense suppression of THL1/2 led to a low level constitutive rejection of all Brassica napus pollen tested. Fluorescence microscopy revealed that the pollen rejection was a typical Brassica self-incompatibility rejection response with reduced pollen adhesion, germination and pollen tube growth. In addition, Westar was found to express the SLG(15) and SRK(15) proteins which may be the target of regulation by THL1 and THL2. Thus, these results indicate that the THL1 and THL2 are required for full pollen acceptance in B. napus cv. Westar.