RESUMO
Staphylococcus aureus RNAIII is one of the main intracellular effectors of the quorum-sensing system. It is a multifunctional RNA that encodes a small peptide, and its noncoding parts act as antisense RNAs to regulate the translation and/or the stability of mRNAs encoding transcriptional regulators, major virulence factors, and cell wall metabolism enzymes. In this review, we explain how regulatory proteins and RNAIII are embedded in complex regulatory circuits to express virulence factors in a dynamic and timely manner in response to stress and environmental and metabolic changes.
Assuntos
Percepção de Quorum , RNA Bacteriano/metabolismo , Regulon , Infecções Estafilocócicas/microbiologia , Staphylococcus aureus/enzimologia , Staphylococcus aureus/patogenicidade , Fatores de Virulência/genética , Animais , Proteínas de Bactérias , Regulação Bacteriana da Expressão Gênica , Humanos , RNA Bacteriano/genética , Staphylococcus aureus/genética , Staphylococcus aureus/fisiologia , Virulência , Fatores de Virulência/metabolismoRESUMO
The virulon of Staphyloccocus aureus is controlled by intricate connections between transcriptional and post-transcriptional regulators including proteins and small non-coding RNAs (sRNAs). Many of the sRNAs regulate gene expression through base-pairings with mRNAs. However, characterization of the direct sRNA targets in Gram-positive bacteria remained a difficult challenge. Here, we have applied and adapted the MS2-affinity purification approach coupled to RNA sequencing (MAPS) to determine the targetome of RsaA sRNA of S. aureus, known to repress the synthesis of the transcriptional regulator MgrA. Several mRNAs were enriched with RsaA expanding its regulatory network. Besides mgrA, several of these mRNAs encode a family of SsaA-like enzymes involved in peptidoglycan metabolism and the secreted anti-inflammatory FLIPr protein. Using a combination of in vivo and in vitro approaches, these mRNAs were validated as direct RsaA targets. Quantitative differential proteomics of wild-type and mutant strains corroborated the MAPS results. Additionally, it revealed that RsaA indirectly activated the synthesis of surface proteins supporting previous data that RsaA stimulated biofilm formation and favoured chronic infections. All together, this study shows that MAPS could also be easily applied in Gram-positive bacteria for identification of sRNA targetome.
Assuntos
Proteínas de Membrana/genética , RNA não Traduzido/fisiologia , Staphylococcus aureus/genética , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Sequência de Bases , Sítios de Ligação , Regulação Bacteriana da Expressão Gênica , Proteínas de Membrana/metabolismo , Proteoma/genética , Proteoma/metabolismo , Interferência de RNA , RNA Bacteriano , RNA Mensageiro , Staphylococcus aureus/metabolismo , TranscriptomaRESUMO
Staphylococcus aureus produces a high number of RNAs for which the functions are poorly understood. Several non-coding RNAs carry a C-rich sequence suggesting that they regulate mRNAs at the post-transcriptional level. We demonstrate that the Sigma B-dependent RsaA RNA represses the synthesis of the global transcriptional regulator MgrA by forming an imperfect duplex with the Shine and Dalgarno sequence and a loop-loop interaction within the coding region of the target mRNA. These two recognition sites are required for translation repression. Consequently, RsaA causes enhanced production of biofilm and a decreased synthesis of capsule formation in several strain backgrounds. These phenotypes led to a decreased protection of S. aureus against opsonophagocytic killing by polymorphonuclear leukocytes compared to the mutant strains lacking RsaA. Mice animal models showed that RsaA attenuates the severity of acute systemic infections and enhances chronic catheter infection. RsaA takes part in a regulatory network that contributes to the complex interactions of S. aureus with the host immune system to moderate invasiveness and favour chronic infections. It is the first example of a conserved small RNA in S. aureus functioning as a virulence suppressor of acute infections. Because S. aureus is essentially a human commensal, we propose that RsaA has been positively selected through evolution to support commensalism and saprophytic interactions with the host.
Assuntos
Regulação Bacteriana da Expressão Gênica/genética , Interações Hospedeiro-Parasita/genética , RNA não Traduzido/genética , Infecções Estafilocócicas/genética , Staphylococcus aureus/genética , Staphylococcus aureus/patogenicidade , Animais , Bacteriemia/genética , Proteínas de Bactérias/genética , Northern Blotting , Western Blotting , Infecções Relacionadas a Cateter/genética , Modelos Animais de Doenças , Feminino , Camundongos , Camundongos Endogâmicos C57BL , Proteômica , RNA Bacteriano/genética , Reação em Cadeia da Polimerase Via Transcriptase Reversa , VirulênciaRESUMO
In Staphylococcus aureus, peptidoglycan metabolism plays a role in the host inflammatory response and pathogenesis. Transcription of the peptidoglycan hydrolases is activated by the essential 2-component system WalKR at low cell density. During stationary growth phase, WalKR is not active and transcription of the peptidoglycan hydrolase genes is repressed. In this work, we studied regulation of expression of the glycylglycine endopeptidase LytM. We show that, in addition to the transcriptional regulation mediated by WalKR, the synthesis of LytM is negatively controlled by a unique mechanism at the stationary growth phase. We have identified 2 different mRNAs encoding lytM, which vary in the length of their 5' untranslated (5'UTR) regions. LytM is predominantly produced from the WalKR-regulated mRNA transcript carrying a short 5'UTR. The lytM mRNA is also transcribed as part of a polycistronic operon with the upstream SA0264 gene and is constitutively expressed. Although SA0264 protein can be synthesized from the longer operon transcript, lytM cannot be translated because its ribosome-binding site is sequestered into a translationally inactive secondary structure. In addition, the effector of the agr system, RNAIII, can inhibit translation of lytM present on the operon without altering the transcript level but does not have an effect on the translation of the upstream gene. We propose that this dual regulation of lytM expression, at the transcriptional and post-transcriptional levels, contributes to prevent cell wall damage during the stationary phase of growth.
Assuntos
N-Acetil-Muramil-L-Alanina Amidase/metabolismo , Staphylococcus aureus/enzimologia , Regiões Promotoras Genéticas , Biossíntese de Proteínas , RNA Mensageiro/genética , Staphylococcus aureus/crescimento & desenvolvimentoRESUMO
Cooperative behaviors among individuals of numerous species play a crucial role in social interactions. There is a special interest in investigating the occurrence of cooperation among apes because this knowledge could also shed light on evolutionary processes and help us understand the origin and development of cooperation in humans and primates in general. Gibbons are phylogenetically intermediate between the great apes and monkeys, and therefore represent a unique opportunity for comparisons. The aim of the present study was to discover whether or not white-handed gibbons (Hylobates lar) show cooperative behaviors. In order to test for the respective behaviors, the gibbons were presented with a commonly used experimental cooperative rope-pulling task. The gibbons in this study did not exhibit cooperative behaviors during the problem-solving task. However, prior training procedures could not be fully completed, hence this project constitutes only the onset of exploring cooperative behaviors in gibbons. Additional behavioral observations revealed that the gibbons spent significantly more time "out of arm's reach to everyone", suggesting that they are less often involved in social interactions, than other, more cooperative primates.
Assuntos
Hominidae , Hylobates , Animais , Humanos , Haplorrinos , Comportamento CooperativoRESUMO
Staphylococcus aureus RNAIII is the intracellular effector of the quorum sensing system that temporally controls a large number of virulence factors including exoproteins and cell-wall-associated proteins. Staphylocoagulase is one major virulence factor, which promotes clotting of human plasma. Like the major cell surface protein A, the expression of staphylocoagulase is strongly repressed by the quorum sensing system at the post-exponential growth phase. Here we used a combination of approaches in vivo and in vitro to analyze the mechanism used by RNAIII to regulate the expression of staphylocoagulase. Our data show that RNAIII represses the synthesis of the protein through a direct binding with the mRNA. Structure mapping shows that two distant regions of RNAIII interact with coa mRNA and that the mRNA harbors a conserved signature as found in other RNAIII-target mRNAs. The resulting complex is composed of an imperfect duplex masking the Shine-Dalgarno sequence of coa mRNA and of a loop-loop interaction occurring downstream in the coding region. The imperfect duplex is sufficient to prevent the formation of the ribosomal initiation complex and to repress the expression of a reporter gene in vivo. In addition, the double-strand-specific endoribonuclease III cleaves the two regions of the mRNA bound to RNAIII that may contribute to the degradation of the repressed mRNA. This study validates another direct target of RNAIII that plays a role in virulence. It also illustrates the diversity of RNAIII-mRNA topologies and how these multiple RNAIII-mRNA interactions would mediate virulence regulation.
Assuntos
Coagulase/genética , Biossíntese de Proteínas/fisiologia , Estabilidade de RNA/fisiologia , RNA Bacteriano/genética , Staphylococcus aureus/genética , Sítios de Ligação/genética , Códon de Iniciação/genética , Regulação Bacteriana da Expressão Gênica , Óperon Lac , Conformação de Ácido Nucleico , RNA Bacteriano/química , RNA Mensageiro/química , RNA Mensageiro/genética , Ribossomos/fisiologia , Staphylococcus aureus/crescimento & desenvolvimento , Staphylococcus aureus/patogenicidade , VirulênciaRESUMO
The endoribonuclease III (RNase III) belongs to the enzyme family known to process double-stranded RNAs. Staphylococcus aureus RNase III was shown to regulate, in concert with the quorum sensing induced RNAIII, the degradation of several mRNAs encoding virulence factors and the transcriptional repressor of toxins Rot. Two of the mRNA-RNAIII complexes involve fully base paired loop-loop interactions with similar sequences that are cleaved by RNase III at a unique position. We show here that the sequence of the base pairs within the loop-loop interaction is not critical for RNase III cleavage, but that the co-axial stacking of three consecutive helices provides an ideal topology for RNase III recognition. In contrast, RNase III induces several strong cleavages in a regular helix, which carries a sequence similar to the loop-loop interaction. The introduction of a bulged loop that interrupts the regular helix restrains the number of cleavages. This work shows that S. aureus RNase III is able to bind and cleave a variety of RNA-mRNA substrates, and that specific structure elements direct the action of RNase III.
Assuntos
Regulação Bacteriana da Expressão Gênica , RNA Bacteriano/metabolismo , Ribonuclease III/metabolismo , Staphylococcus aureus/enzimologia , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Ativação Enzimática , Modelos Moleculares , Mutagênese Sítio-Dirigida , Conformação de Ácido Nucleico , Porinas/genética , Porinas/metabolismo , Ligação Proteica , Biossíntese de Proteínas , Mapeamento de Interação de Proteínas , Percepção de Quorum , Estabilidade de RNA , RNA Antissenso/genética , RNA Antissenso/metabolismo , RNA Bacteriano/genética , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Ribonuclease III/genética , Staphylococcus aureus/genética , Relação Estrutura-AtividadeRESUMO
Bioinformatic analysis of the intergenic regions of Staphylococcus aureus predicted multiple regulatory regions. From this analysis, we characterized 11 novel noncoding RNAs (RsaA-K) that are expressed in several S. aureus strains under different experimental conditions. Many of them accumulate in the late-exponential phase of growth. All ncRNAs are stable and their expression is Hfq-independent. The transcription of several of them is regulated by the alternative sigma B factor (RsaA, D and F) while the expression of RsaE is agrA-dependent. Six of these ncRNAs are specific to S. aureus, four are conserved in other Staphylococci, and RsaE is also present in Bacillaceae. Transcriptomic and proteomic analysis indicated that RsaE regulates the synthesis of proteins involved in various metabolic pathways. Phylogenetic analysis combined with RNA structure probing, searches for RsaE-mRNA base pairing, and toeprinting assays indicate that a conserved and unpaired UCCC sequence motif of RsaE binds to target mRNAs and prevents the formation of the ribosomal initiation complex. This study unexpectedly shows that most of the novel ncRNAs carry the conserved C-rich motif, suggesting that they are members of a class of ncRNAs that target mRNAs by a shared mechanism.
Assuntos
Regulação Bacteriana da Expressão Gênica , RNA não Traduzido/química , Staphylococcus aureus/genética , Bacillus subtilis/genética , Bacillus subtilis/metabolismo , Sequência de Bases , Biologia Computacional , Sequência Conservada , Perfilação da Expressão Gênica , Dados de Sequência Molecular , Proteômica , Estabilidade de RNA , RNA Mensageiro/metabolismo , RNA não Traduzido/genética , RNA não Traduzido/metabolismo , Transcrição GênicaRESUMO
This is the first study of vocal individuality in male songs of black crested gibbons. The sound recordings were carried out at two field sites, Pinghe, Ailao Mountains, and Dazhaizi, Wuliang Mountains, both located in Yunnan province, China. A total of 127 coda phrases of 38 male songs bouts of eight individual male gibbons were analyzed. Stepwise discriminant function analysis was used to examine the acoustic individuality of the males. We found that individuality among neighbors was very pronounced. Moreover, individuality within a site (i.e. among neighbors) is higher than among individuals between sites. Our finding suggests that black crested gibbons may actively increase their degree of vocal individuality against that of their immediate neighbors by vocal adjustment.
Assuntos
Hylobatidae/psicologia , Vocalização Animal , Animais , China , Análise Discriminante , Meio Ambiente , Individualidade , Masculino , Espectrografia do Som/veterináriaRESUMO
We describe a snub-nosed monkey that is new to science from the high altitudes of northeastern Kachin state, northeastern Myanmar, the Burmese snub-nosed monkey, Rhinopithecus strykeri sp. nov. Descriptions are based on a skin and skulls of four specimens obtained from local hunters. The new species is geographically isolated from other snub-nosed monkeys and separated from them by two major barriers--the Mekong and the Salween (Thanlwin) rivers. The species is chiefly diagnosed by its almost entirely blackish fur coloration with white fur only on ear tufts, chin beard, and perineal area, and its relatively long tail (140% of head and body length in the adult male). Preliminary surveys and interviews with hunters indicate that the new species is limited in distribution to the Maw River area, a small region of the Salween-N'mai Hka divide in northeastern Kachin state, northeastern Myanmar. The distribution area appears to cover about 270 km(2), and the species may consist of only three groups with a total population of approximately 260-330 individuals. Our data on hunting pressure suggest that the species is Critically Endangered.
Assuntos
Colobinae/classificação , Animais , Biodiversidade , Tamanho Corporal , Colobinae/anatomia & histologia , Conservação dos Recursos Naturais , Espécies em Perigo de Extinção , Meio Ambiente , Feminino , Geografia , Masculino , Mianmar , Densidade Demográfica , ÁrvoresRESUMO
Pigmentation patterns of the visible part of the eyeball, encompassing the iris and portions of the sclera, have been discussed to be linked to social cognition in primates. The cooperative eye hypothesis suggests the white sclera of humans to be a derived adaptive trait that enhances eye-mediated communication. Here, we provide a comparative analysis of ocular pigmentation patterns in 15 species of hominoids (humans, great apes & gibbons) that show marked differences in social cognition and quantify scleral exposure at the genus level. Our data reveals a continuum of eye pigmentation traits in hominoids which does not align with the complexity of gaze-mediated communication in the studied taxa. Gibbons display darker eyes than great apes and expose less sclera. Iridoscleral contrasts in orangutans and gorillas approach the human condition but differ between congeneric species. Contrary to recent discussions, we found chimpanzee eyes to exhibit a cryptic coloration scheme that resembles gibbons more than other apes. We reevaluate the evidence for links between social cognition and eye pigmentation in primates, concluding that the cooperative eye hypothesis cannot explain the patterns observed. Differences in scleral pigmentation between great apes and humans are gradual and might have arisen via genetic drift and sexual selection.
Assuntos
Comunicação Animal , Hominidae , Hylobates , Iris , Epitélio Pigmentado Ocular , Animais , Evolução Biológica , Humanos , Filogenia , Característica Quantitativa HerdávelRESUMO
BACKGROUND: Gibbons or small apes inhabit tropical and subtropical rain forests in Southeast Asia and adjacent regions, and are, next to great apes, our closest living relatives. With up to 16 species, gibbons form the most diverse group of living hominoids, but the number of taxa, their phylogenetic relationships and their phylogeography is controversial. To further the discussion of these issues we analyzed the complete mitochondrial cytochrome b gene from 85 individuals representing all gibbon species, including most subspecies. RESULTS: Based on phylogenetic tree reconstructions, several monophyletic clades were detected, corresponding to genera, species and subspecies. A significantly supported branching pattern was obtained for members of the genus Nomascus but not for the genus Hylobates. The phylogenetic relationships among the four genera were also not well resolved. Nevertheless, the new data permitted the estimation of divergence ages for all taxa for the first time and showed that most lineages emerged during four short time periods. In the first, between approximately 6.7 and approximately 8.3 mya, the four gibbon genera diverged from each other. In the second (approximately 3.0 - approximately 3.9 mya) and in the third period (approximately 1.3 - approximately 1.8 mya), Hylobates and Hoolock differentiated. Finally, between approximately 0.5 and approximately 1.1 mya, Hylobates lar diverged into subspecies. In contrast, differentiation of Nomascus into species and subspecies was a continuous and prolonged process lasting from approximately 4.2 until approximately 0.4 mya. CONCLUSIONS: Although relationships among gibbon taxa on various levels remain unresolved, the present study provides a more complete view of the evolutionary and biogeographic history of the hylobatid family, and a more solid genetic basis for the taxonomic classification of the surviving taxa. We also show that mtDNA constitutes a useful marker for the accurate identification of individual gibbons, a tool which is urgently required to locate hunting hotspots and select individuals for captive breeding programs. Further studies including nuclear sequence data are necessary to completely understand the phylogeny and phylogeography of gibbons.
Assuntos
Evolução Biológica , DNA Mitocondrial/genética , Hylobates/genética , Animais , Sudeste Asiático , Espécies em Perigo de Extinção , Hylobates/classificação , FilogeniaRESUMO
Enzymatic probing and lead(II)-induced cleavages have been developed to study the secondary structure of RNA molecules either free or engaged in complex with different ligands. Using a combination of probes with different specificities (unpaired vs. paired regions), it is possible to get information on the accessibility of each nucleotide, on the binding site of a ligand (noncoding RNAs, protein, metabolites), and on RNA conformational changes that accompanied ligand binding or environmental conditions (temperature, pH, ions, etc.). The detection of the cleavages can be conducted by two different ways, which are chosen according to the length of the studied RNA. The first method uses end-labeled RNA molecules and the second one involves primer extension by reverse transcriptase. We provide here an experimental procedure that was designed to map the structure of mRNA and mRNA-sRNA interaction in vitro.
Assuntos
Enzimas/metabolismo , Chumbo/farmacologia , Biologia Molecular/métodos , RNA Mensageiro/química , RNA Mensageiro/metabolismo , RNA não Traduzido/metabolismo , Staphylococcus aureus/metabolismo , Sequência de Bases , Fracionamento Químico , Hidrólise/efeitos dos fármacos , Dados de Sequência Molecular , Conformação de Ácido Nucleico/efeitos dos fármacos , RNA/metabolismo , RNA Bacteriano/síntese química , RNA Mensageiro/genética , RNA não Traduzido/química , RNA não Traduzido/genética , Staphylococcus aureus/efeitos dos fármacosRESUMO
During the past few years, our knowledge on RNA-based regulation in many organisms has tremendously increased. In bacteria, although transcriptional regulatory proteins remain key players in gene regulation, a wide variety of post-transcriptional regulatory mechanisms discovered highlights the importance of the mRNA structure in the regulation of gene expression. RNA-dependent regulation largely contributes to rapidly adapt the bacterial metabolism in response to environmental changes, stress and in establishment of virulence. Bacteria exploit the extraordinary ability of mRNA to fold into different structures in response to various signals (environmental cues, ligand binding). Induced mRNA conformational rearrangements can potentially regulate transcription, translation and mRNA stability. The present review focuses on the structures of regulatory regions of mRNA that have evolved to permit productive interactions with trans-acting regulators, such as protein or non-coding RNAs. Finally, we describe how particular properties of these regulatory complexes regulate translation initiation.
Assuntos
Bactérias/genética , Conformação de Ácido Nucleico , Biossíntese de Proteínas , RNA Mensageiro/química , Sequência de Aminoácidos , Proteínas de Bactérias/química , Proteínas de Bactérias/genética , Dados de Sequência Molecular , Homologia de Sequência de AminoácidosRESUMO
To identify noncoding RNAs (ncRNAs) in the pathogenic bacterium Listeria monocytogenes, we analyzed the intergenic regions (IGRs) of strain EGD-e by in silico-based approaches. Among the twelve ncRNAs found, nine are novel and specific to the Listeria genus, and two of these ncRNAs are expressed in a growth-dependent manner. Three of the ncRNAs are transcribed in opposite direction to overlapping open reading frames (ORFs), suggesting that they act as antisense on the corresponding mRNAs. The other ncRNA genes appear as single transcription units. One of them displays five repeats of 29 nucleotides. Five of these new ncRNAs are absent from the non-pathogenic species L. innocua, raising the possibility that they might be involved in virulence. To predict mRNA targets of the ncRNAs, we developed a computational method based on thermodynamic pairing energies and known ncRNA-mRNA hybrids. Three ncRNAs, including one of the putative antisense ncRNAs, were predicted to have more than one mRNA targets. Several of them were shown to bind efficiently to the ncRNAs suggesting that our in silico approach could be used as a general tool to search for mRNA targets of ncRNAs.
Assuntos
Listeria monocytogenes/genética , RNA Mensageiro/metabolismo , RNA não Traduzido/genética , Região 5'-Flanqueadora , Sequência de Bases , Biologia Computacional , DNA Intergênico/química , Ensaio de Desvio de Mobilidade Eletroforética , Genes Bacterianos , Genômica , Listeria monocytogenes/metabolismo , Dados de Sequência Molecular , RNA Mensageiro/química , RNA não Traduzido/análise , RNA não Traduzido/metabolismoAssuntos
Viabilidade Microbiana/genética , RNA não Traduzido/fisiologia , Staphylococcus aureus/patogenicidade , Virulência/genética , Biofilmes/crescimento & desenvolvimento , Regulação para Baixo , Regulação Bacteriana da Expressão Gênica , Humanos , Infecções Estafilocócicas/genética , Infecções Estafilocócicas/microbiologia , Staphylococcus aureus/genética , Staphylococcus aureus/crescimento & desenvolvimentoRESUMO
We carried out a short study on the diurnal call distribution of two sympatric lemurs in the Réserve Naturelle Intégrale Zahamena (eastern Madagascar). Whereas indris (Indri) song bouts were clearly concentrated in the early morning hours, the roar/shriek choruses of ruffed lemurs (Varecia) exhibited a much more even distribution throughout the day. These differences in distribution pattern support earlier claims that indri song bouts are more likely to serve territorial functions, whereas ruffed lemur loud calls may serve both spacing and/or alarm call functions.
Assuntos
Comportamento Social , Strepsirhini/psicologia , Territorialidade , Vocalização Animal , Animais , Lemuridae/psicologia , Fatores de TempoRESUMO
From studies of both wild and captive animals, gibbons are thought to reach sexual maturity at about 6 to 8 years of age, and the siamang (Hylobates syndactylus) at about 8 to 9 years. However, a review of the literature reveals that in most cases the exact age of the maturing animals was not known and had to be estimated. This study presents seven case reports on captive gibbons of known age. Captive males of the white-cheeked crested gibbon (H. leucogenys leucogenys) and of the siamang (H. syndactylus) can breed at the age of 4 and 4.3 years, respectively. Similarly, hybrid females (H. lar × H. moloch) and siamang females can breed at 5.1 and 5.2 years, respectively. This finding may help to improve the breeding success of captive gibbon populations. It is not clear whether gibbons reach sexual maturity earlier in captivity or whether sexual maturity is also reached by 5 years of age in the wild. Possible implications for the interpretation of group size regulation and of reproductive strategies of wild gibbons are discussed.