RESUMEN
Excessive expansions of glutamine (Q)-rich repeats in various human proteins are known to result in severe neurodegenerative disorders such as Huntington's disease and several ataxias. However, the physiological role of these repeats and the consequences of more moderate repeat variation remain unknown. Here, we demonstrate that Q-rich domains are highly enriched in eukaryotic transcription factors where they act as functional modulators. Incremental changes in the number of repeats in the yeast transcriptional regulator Ssn6 (Cyc8) result in systematic, repeat-length-dependent variation in expression of target genes that result in direct phenotypic changes. The function of Ssn6 increases with its repeat number until a certain threshold where further expansion leads to aggregation. Quantitative proteomic analysis reveals that the Ssn6 repeats affect its solubility and interactions with Tup1 and other regulators. Thus, Q-rich repeats are dynamic functional domains that modulate a regulator's innate function, with the inherent risk of pathogenic repeat expansions.
Asunto(s)
Proteínas Represoras/metabolismo , Proteínas de Saccharomyces cerevisiae/metabolismo , Saccharomyces cerevisiae/metabolismo , Secuencia de Bases , ADN de Hongos/genética , Regulación Fúngica de la Expresión Génica , Glutamina/química , Datos de Secuencia Molecular , Dominios y Motivos de Interacción de Proteínas , Estabilidad Proteica , Secuencias Repetitivas de Aminoácido , Proteínas Represoras/química , Proteínas Represoras/genética , Saccharomyces cerevisiae/genética , Proteínas de Saccharomyces cerevisiae/química , Proteínas de Saccharomyces cerevisiae/genética , SolubilidadRESUMEN
Genotype-to-phenotype mapping commonly focuses on two major classes of mutations: single nucleotide polymorphisms (SNPs) and copy number variation (CNV). Here, we discuss an underestimated third class of genotypic variation: changes in microsatellite and minisatellite repeats. Such tandem repeats (TRs) are ubiquitous, unstable genomic elements that have historically been designated as nonfunctional "junk DNA" and are therefore mostly ignored in comparative genomics. However, as many as 10% to 20% of eukaryotic genes and promoters contain an unstable repeat tract. Mutations in these repeats often have fascinating phenotypic consequences. For example, changes in unstable repeats located in or near human genes can lead to neurodegenerative diseases such as Huntington disease. Apart from their role in disease, variable repeats also confer useful phenotypic variability, including cell surface variability, plasticity in skeletal morphology, and tuning of the circadian rhythm. As such, TRs combine characteristics of genetic and epigenetic changes that may facilitate organismal evolvability.
Asunto(s)
Evolución Molecular , Repeticiones de Microsatélite , Repeticiones de Minisatélite , Secuencias Reguladoras de Ácidos Nucleicos , Animales , Humanos , Enfermedades Neurodegenerativas/genéticaRESUMEN
Tandem repeats are short DNA sequences that are repeated head-to-tail with a propensity to be variable. They constitute a significant proportion of the human genome, also occurring within coding and regulatory regions. Variation in these repeats can alter the function and/or expression of genes allowing organisms to swiftly adapt to novel environments. Importantly, some repeat expansions have also been linked to certain neurodegenerative diseases. Therefore, accurate sequencing of tandem repeats could contribute to our understanding of common phenotypic variability and might uncover missing genetic factors in idiopathic clinical conditions. However, despite long-standing evidence for the functional role of repeats, they are largely ignored because of technical limitations in sequencing, mapping and typing. Here, we report on a novel capture technique and data filtering protocol that allowed simultaneous sequencing of thousands of tandem repeats in the human genomes of a three generation family using GS-FLX-plus Titanium technology. Our results demonstrated that up to 7.6% of tandem repeats in this family (4% in coding sequences) differ from the reference sequence, and identified a de novo variation in the family tree. The method opens new routes to look at this underappreciated type of genetic variability, including the identification of novel disease-related repeats.
Asunto(s)
Genoma Humano , Polimorfismo Genético , Secuencias Repetidas en Tándem , Secuencia de Bases , Femenino , Componentes del Gen , Humanos , Masculino , Datos de Secuencia Molecular , Linaje , Análisis de Secuencia de ADNRESUMEN
Giving effective and interesting talks are key skills for scientists at every stage of their career. This installment of the Words of Advice series provides some insights into preparing and delivering compelling presentations, as well as alleviating pretalk nerves.
Asunto(s)
Comunicación , Presentación de Datos , Guías como Asunto/normas , Difusión de la Información/métodos , Habla , Recursos Audiovisuales , HumanosRESUMEN
Ribulosamines, which are substrates for the deglycating enzyme fructosamine-3-kinase-related protein, are presumably formed intracellularly through glycation of proteins with ribose 5-phosphate followed by dephosphorylation of resulting RN5Ps (ribulosamine 5-phosphates) by a putative RN5Pase (ribulosamine-5-phosphatase). Ribose 5-phosphate is known to be a potent glycating agent and we show in the present study that it reacts approximately 10 and 80-fold more rapidly with protein than ribose and glucose respectively. We also show that tissue extracts and, most particularly, erythrocyte extracts contain a protein-RN5Pase. We have purified this enzyme from human erythrocytes to near homogeneity and shown it to correspond to LMWPTP-A [low-molecular-mass ('weight') protein tyrosine phosphatase-A]. Human recombinant LMWPTP-A displayed an RN5Pase activity that was higher than its tyrosine phosphatase activity, indicating that this phosphatase may participate in protein deglycation, a new form of protein repair.
Asunto(s)
Fosfoproteínas Fosfatasas/metabolismo , Proteínas Tirosina Fosfatasas/metabolismo , Receptores de Superficie Celular/metabolismo , Secuencia de Aminoácidos , Animales , Eritrocitos/enzimología , Glicosilación , Humanos , Masculino , Datos de Secuencia Molecular , Peso Molecular , Fosfoproteínas Fosfatasas/química , Fosfoproteínas Fosfatasas/aislamiento & purificación , Fosforilación , Fosfotransferasas (Aceptor de Grupo Alcohol)/metabolismo , Proteínas Tirosina Fosfatasas/química , Proteínas Tirosina Fosfatasas/aislamiento & purificación , Ratas , Ratas Wistar , Proteínas Tirosina Fosfatasas Clase 4 Similares a Receptores , Receptores de Superficie Celular/química , Receptores de Superficie Celular/aislamiento & purificación , Ribosamonofosfatos/metabolismo , Especificidad por Sustrato , Distribución TisularRESUMEN
Poster sessions are an important forum for getting feedback on your results and engaging with the scientific community. In this instalment of the Words of Advice series, we provide you with a guide to designing an outstanding poster and offer tips on how to effectively communicate your results using your poster.
Asunto(s)
Carteles como Asunto , Proyectos de InvestigaciónRESUMEN
The purpose of this work was to identify the function of bacterial homologues of fructosamine 3-kinase (FN3K), a mammalian enzyme responsible for the removal of fructosamines from proteins. FN3K homologues were identified in approximately 200 (i.e. approximately 27%) of the sequenced bacterial genomes. In 11 of these genomes, from phylogenetically distant bacteria, the FN3K homologue was immediately preceded by a low-molecular-weight protein-tyrosine-phosphatase (LMW-PTP) homologue, which is therefore probably functionally related to the FN3K homologue. Five bacterial FN3K homologues (from Escherichia coli, Enterococcus faecium, Lactobacillus plantarum, Staphylococcus aureus and Thermus thermophilus) were overexpressed in E. coli, purified and their kinetic properties investigated. Four were ribulosamine/erythrulosamine 3-kinases acting best on free lysine and cadaverine derivatives, but not on ribulosamines bound to the alpha amino group of amino acids. They also phosphorylated protein-bound ribulosamines or erythrulosamines, but not protein-bound fructosamines, therefore having properties similar to those of mammalian FN3K-related protein. The E. coli FN3K homologue (YniA) was inactive on all tested substrates. The LMW-PTP of T. thermophilus, which forms an operon with an FN3K homologue, and an LMW-PTP of S. aureus (PtpA) were overexpressed in E. coli, purified and shown to dephosphorylate not only protein tyrosine phosphates, but protein ribulosamine 5-phosphates as well as free ribuloselysine 5-phosphate and erythruloselysine 4-phosphate. These LMW-PTPs were devoid of ribulosamine 3-phosphatase activity. It is concluded that most bacterial FN3K homologues are ribulosamine/erythrulosamine 3-kinases. They may serve, in conjunction with a phosphatase, to deglycate products of glycation formed from ribose 5-phosphate or erythrose 4-phosphate.
Asunto(s)
Proteínas de Arabidopsis/metabolismo , Bacterias/enzimología , Proteínas Bacterianas/metabolismo , Glucosa/metabolismo , Fosfotransferasas (Aceptor de Grupo Alcohol)/metabolismo , Secuencia de Aminoácidos , Bacterias/clasificación , Bacterias/genética , Proteínas Bacterianas/química , Genoma Bacteriano , Datos de Secuencia Molecular , Peso Molecular , Homología de Secuencia de Aminoácido , Especificidad de la EspecieRESUMEN
In the second part of our Words of Advice on science careers, we bring you the perspectives of established scientists who enjoy successful, fulfilling careers in academia, the patent office and a publishing company. We also get the thoughts of a PhD student on her internship at The FEBS Journal's Editorial Office. Get inspired by these scientists and trace your own path towards a rewarding science career.
Asunto(s)
Selección de Profesión , Investigadores , Ciencia , Educación de Postgrado , Humanos , Internado no MédicoRESUMEN
Understanding the dynamic behaviour of the Plasmodium falciparum metabolism during infection can help identify targets for drug development. In this Commentary, we highlight recently published studies in The FEBS Journal that cover mathematical modelling of glycolysis in P. falciparum and the identification and in vivo validation of metabolic drug targets.
Asunto(s)
Antimaláricos/uso terapéutico , Malaria/tratamiento farmacológico , Modelos Teóricos , Antimaláricos/farmacología , Glucólisis/efectos de los fármacos , Humanos , Plasmodium falciparum/efectos de los fármacos , Plasmodium falciparum/metabolismoRESUMEN
In this instalment of the Words of Advice series, PhD-level scientists working in a wide range of disciplines share with us their insider's view on their roles, the steps they took to enter these professions and the attributes needed for a successful career.
Asunto(s)
Investigación Biomédica , Selección de Profesión , Movilidad Laboral , Humanos , Enseñanza , Recursos HumanosRESUMEN
Accurate and clear representation of scientific data is essential for the advancement of science. In this instalment of the Words of Advice series, we feature guidelines and tips on best practices for writing manuscripts, designing experiments and preparing figures and images for publication.
Asunto(s)
Investigación Biomédica/educación , Ilustración Médica/educación , Publicaciones Periódicas como Asunto/normas , Rol Profesional , Investigadores/educación , Escritura , Investigación Biomédica/tendencias , Humanos , Publicaciones Periódicas como Asunto/tendencias , Autonomía Personal , Plagio , Autonomía Profesional , Reproducibilidad de los Resultados , Proyectos de Investigación/normas , Proyectos de Investigación/tendencias , Investigadores/tendencias , Programas Informáticos , Recursos Humanos , Escritura/normasRESUMEN
Writing a competitive grant application is an essential skill for any scientist who wants to embark on an independent career. This instalment of the Words of Advice series provides a comprehensive guide to preparing a successful grant or personal fellowship application.
Asunto(s)
Investigación Biomédica/economía , Investigación Biomédica/normas , Organización de la Financiación/normas , Apoyo a la Investigación como Asunto , Escritura/normas , Becas , HumanosRESUMEN
Proteins with amino acid homorepeats have the potential to be detrimental to cells and are often associated with human diseases. Why, then, are homorepeats prevalent in eukaryotic proteomes? In yeast, homorepeats are enriched in proteins that are essential and pleiotropic and that buffer environmental insults. The presence of homorepeats increases the functional versatility of proteins by mediating protein interactions and facilitating spatial organization in a repeat-dependent manner. During evolution, homorepeats are preferentially retained in proteins with stringent proteostasis, which might minimize repeat-associated detrimental effects such as unregulated phase separation and protein aggregation. Their presence facilitates rapid protein divergence through accumulation of amino acid substitutions, which often affect linear motifs and post-translational-modification sites. These substitutions may result in rewiring protein interaction and signaling networks. Thus, homorepeats are distinct modules that are often retained in stringently regulated proteins. Their presence facilitates rapid exploration of the genotype-phenotype landscape of a population, thereby contributing to adaptation and fitness.
Asunto(s)
Proteínas/genética , Proteínas/metabolismo , Secuencias Repetitivas de Aminoácido/genética , Evolución Biológica , Eucariontes , Mapas de Interacción de ProteínasRESUMEN
Ubiquitin conjugation signals for selective protein degradation by the proteasome. In eukaryotes, ubiquitin is encoded both as a monomeric ubiquitin unit fused to a ribosomal gene and as multiple ubiquitin units in tandem. The polyubiquitin gene is a unique, highly conserved open reading frame composed solely of tandem repeats, yet it is still unclear why cells utilize this unusual gene structure. Using the Saccharomyces cerevisiae UBI4 gene, we show that this multi-unit structure allows cells to rapidly produce large amounts of ubiquitin needed to respond to sudden stress. The number of ubiquitin units encoded by UBI4 influences cellular survival and the rate of ubiquitin-proteasome system (UPS)-mediated proteolysis following heat stress. Interestingly, the optimal number of repeats varies under different types of stress indicating that natural variation in repeat numbers may optimize the chance for survival. Our results demonstrate how a variable polycistronic transcript provides an evolutionary alternative for gene copy number variation.Eukaryotic cells rely on the ubiquitin-proteasome system for selective degradation of proteins, a process vital to organismal fitness. Here the authors show that the number of repeats in the polyubiquitin gene is evolutionarily unstable within and between yeast species, and that this variability may tune the cell's capacity to respond to sudden environmental perturbations.
Asunto(s)
Poliubiquitina/metabolismo , Proteínas de Saccharomyces cerevisiae/genética , Saccharomyces cerevisiae/genética , Ubiquitina C/genética , Evolución Biológica , Clonación Molecular , Variaciones en el Número de Copia de ADN , Dosificación de Gen , Genes Fúngicos , Proteínas Fluorescentes Verdes/metabolismo , Calor , Poliubiquitina/genética , Complejo de la Endopetidasa Proteasomal/metabolismo , Proteostasis , Saccharomyces cerevisiae/metabolismo , Proteínas de Saccharomyces cerevisiae/metabolismo , Ubiquitina C/metabolismoRESUMEN
FN3K (fructosamine 3-kinase) is a mammalian enzyme that catalyses the phosphorylation of fructosamines, which thereby becomes unstable and detaches from proteins. The homologous mammalian enzyme, FN3K-RP (FN3K-related protein), does not phosphorylate fructosamines but ribulosamines, which are probably formed through a spontaneous reaction of amines with ribose 5-phosphate, an intermediate of the pentose-phosphate pathway and the Calvin cycle. We show in the present study that spinach leaf extracts display a substantial ribulosamine kinase activity (approx. 700 times higher than the specific activity of FN3K in erythrocytes). The ribulosamine kinase was purified approx. 400 times and shown to phosphorylate ribulose-epsilon-lysine, protein-bound ribulosamines and also, with higher affinity, erythrulose-epsilon-lysine and protein-bound erythrulosamines. Evidence is presented for the fact that the third carbon of the sugar portion is phosphorylated by this enzyme and that this leads to the formation of unstable compounds decomposing with half-lives of approx. 30 min at 37 degrees C (ribulosamine 3-phosphates) and 5 min at 30 degrees C (erythrulosamine 3-phosphates). This decomposition results in the formation of a 2-oxo-3-deoxyaldose and inorganic phosphate, with regeneration of the free amino group. The Arabidopsis thaliana homologue of FN3K/FN3K-RP was overexpressed in Escherichia coli and shown to have properties similar to those of the enzyme purified from spinach leaves. These results indicate that the plant FN3K/FN3K-RP homologue, which appears to be targeted to the chloroplast in many species, is a ribulosamine/erythrulosamine 3-kinase. This enzyme may participate in a protein deglycation process removing Amadori products derived from ribose 5-phosphate and erythrose 4-phosphate, two Calvin cycle intermediates that are potent glycating agents.
Asunto(s)
Proteínas de Arabidopsis/metabolismo , Arabidopsis/enzimología , Fosfotransferasas (Aceptor de Grupo Alcohol)/metabolismo , Spinacia oleracea/enzimología , Secuencia de Aminoácidos , Amino Azúcares/metabolismo , Proteínas de Arabidopsis/aislamiento & purificación , Semivida , Cinética , Lisina/análogos & derivados , Lisina/metabolismo , Datos de Secuencia Molecular , Pentosas/análogos & derivados , Pentosas/metabolismo , Fosforilación , Fosfotransferasas (Aceptor de Grupo Alcohol)/aislamiento & purificación , Hojas de la Planta/enzimología , Homología de Secuencia de Aminoácido , Especificidad por Sustrato , Tetrosas/análogos & derivados , Tetrosas/metabolismoRESUMEN
In the first instalment of the Words of Advice series, we feature the essentials of good manuscript writing with practical tips on how to plan, organise and write a standout scientific paper.
Asunto(s)
Manuscritos como Asunto , Informe de Investigación/normas , Ciencia/métodos , Escritura/normas , Humanos , Edición/normas , Ciencia/educaciónRESUMEN
Dermal papilla (DP) are specialised mesenchymal cells that activate the formation of new hair follicles. In this issue of The FEBS Journal, Zhang and colleagues show that enhancing the ß-catenin signalling pathway in DP cells allows faster and denser hair growth, providing a potential target for hair loss treatments and for improving hair regeneration techniques.
Asunto(s)
Dermis/metabolismo , beta Catenina/metabolismo , Cabello , Folículo Piloso , Humanos , Transducción de SeñalRESUMEN
Copy Number Variations (CNVs) and Single Nucleotide Polymorphisms (SNPs) have been the major focus of most large-scale comparative genomics studies to date. Here, we discuss a third, largely ignored, type of genetic variation, namely changes in tandem repeat number. Historically, tandem repeats have been designated as non functional "junk" DNA, mostly as a result of their highly unstable nature. With the exception of tandem repeats involved in human neurodegenerative diseases, repeat variation was often believed to be neutral with no phenotypic consequences. Recent studies, however, have shown that as many as 10% to 20% of coding and regulatory sequences in eukaryotes contain an unstable repeat tract. Contrary to initial suggestions, tandem repeat variation can have useful phenotypic consequences. Examples include rapid variation in microbial cell surface, tuning of internal molecular clocks in flies and the dynamic morphological plasticity in mammals. As such, tandem repeats can be useful functional elements that facilitate evolvability and rapid adaptation.