RESUMO
The 2016-2017 epidemic of influenza A (H7N9) virus in China prompted concern that a genetic change may underlie increased virulence. Based on an evolutionary analysis of H7N9 viruses from all five outbreak waves, we find that additional subclades of the H7 and N9 genes have emerged. Our analysis indicates that H7N9 viruses inherited NP genes from co-circulating H7N9 instead of H9N2 viruses. Genotypic diversity among H7N9 viruses increased following wave I, peaked during wave III, and rapidly deceased thereafter with minimal diversity in wave V, suggesting that the viruses entered a relatively stable evolutionary stage. The ZJ11 genotype caused the majority of human infections in wave V. We suggest that the largest outbreak of wave V may be due to a constellation of genes rather than a single mutation. Therefore, continuous surveillance is necessary to minimize the threat of H7N9 viruses.
Assuntos
Subtipo H7N9 do Vírus da Influenza A/genética , Influenza Humana/patologia , Substituição de Aminoácidos , Antígenos/genética , Antígenos/imunologia , Antígenos/metabolismo , China/epidemiologia , Surtos de Doenças , Evolução Molecular , Genótipo , Humanos , Subtipo H7N9 do Vírus da Influenza A/isolamento & purificação , Subtipo H7N9 do Vírus da Influenza A/patogenicidade , Influenza Humana/epidemiologia , Influenza Humana/virologia , Proteínas do Nucleocapsídeo , Filogenia , Proteínas de Ligação a RNA/classificação , Proteínas de Ligação a RNA/genética , RNA Polimerase Dependente de RNA/classificação , RNA Polimerase Dependente de RNA/genética , Proteínas do Core Viral/classificação , Proteínas do Core Viral/genética , Proteínas Virais/classificação , Proteínas Virais/genéticaRESUMO
Trypanosomes, protozoan parasites of the order Kinetoplastida, control gene expression essentially through post-transcriptional mechanisms. Several motifs located mainly in the 3' untranslated region, such as AU-rich elements (AREs), were recently shown to modulate mRNA half-life, and are able to modify mRNA abundance in vivo through the interaction with specific RNA-binding proteins. Along with the detection of an active exosome, decapping activities and a regulated 3' to 5' exonuclease activity stimulated by AREs, these results suggest that modulation of mRNA stability is essential in trypanosomes. These regulatory processes are specific for different developmental stages and thus relevant for allowing trypanosomes to adapt to variable environmental conditions.
Assuntos
Estabilidade de RNA , RNA Mensageiro/metabolismo , RNA de Protozoário/metabolismo , Proteínas de Ligação a RNA/fisiologia , Trypanosoma/genética , Animais , Regulação da Expressão Gênica , Modelos Genéticos , RNA Mensageiro/genética , Proteínas de Ligação a RNA/classificação , Transcrição Gênica/genética , Trypanosoma/classificação , Trypanosoma/metabolismoRESUMO
A full length cDNA for an RNA-binding protein (axolotl RBP) with consensus sequence (RNP-CS) from the Mexican axolotl, Ambystoma mexicanum, has been cloned from a subtraction library. In vitro translation with synthetic mRNA and subsequent hybrid-arrested translation with a specific antisense oligonucleotide confirms that the axolotl RBP cDNA encodes an approx. 16 kDa polypeptide. Computer-assisted analyses revealed amino acid similarities of 58-60% to various RNA-binding proteins and a 90 amino acid region at the amino-terminal end constituting the putative RNA-binding domain (RNP-CS) with two highly conserved motifs, RNP2 and RNP1. Phylogenetic analysis suggests that the putative RNA-binding protein from axolotl is unique. A binding assay with radiolabeled axolotl RBP showed that this RNA-binding protein bound strongly with poly(A) and to a lesser degree with poly(U), but not at all with poly(G), poly(C), or DNA.