RESUMO
Honey bee (Apis mellifera) adult workers change behaviors and nutrition according to age progression. Young workers, such as nurses, perform in-hive tasks and consume protein-rich pollen, while older workers (foragers) leave the colony to search for food, and consume carbohydrate-rich nectar. These environmentally stimulated events involve transcriptional and DNA epigenetic marks alterations in worker tissues. However, post-transcriptional RNA modifications (epitranscriptomics) are still poorly explored in bees. We investigated the transcriptional profiles of m6A and m5C RNA methyltransferases in the brain and fat body of adult workers of 1) different ages and performing different tasks [nurses of 8 days-old (N-8D) and foragers of 29 days-old (F-29D), sampled from wild-type colonies], and 2) same-aged young workers caged in an incubator and treated with a pollen-rich [PR] or a pollen-deprived [PD] diet for 8 days. In the brain, METTL3, DNMT2, NOP2, NSUN2, NSUN5, and NSUN7 genes increased expression during adulthood (from N-8D to F-29D), while the opposite pattern was observed in the fat body for METTL3, DNMT2, and NSUN2 genes. Regarding diet treatments, high expression levels were observed in the brains of the pollen-deprived group (DNMT2, NOP2, and NSUN2 genes) and the fat bodies of the pollen-rich group (NOP2, NSUN4, and NSUN5 genes) compared to the brains of the PR group and the fat bodies of the PD group, respectively. Our data indicate that RNA epigenetics may be an important regulatory layer in the development of adult workers, presenting tissue-specific signatures of RNA methyltransferases expression in response to age, behavior, and diet content.
RESUMO
The causative agent of COVID-19 pandemic, SARS-CoV-2, has a 29,903 bases positive-sense single-stranded RNA genome. RNAs exhibit about 150 modified bases that are essential for proper function. Among internal modified bases, the N6-methyladenosine, or m6A, is the most frequent, and is implicated in SARS-CoV-2 immune response evasion. Although the SARS-CoV-2 genome is RNA, almost all genomes sequenced thus far are, in fact, reverse transcribed complementary DNAs. This process reduces the true complexity of these viral genomes because the incorporation of dNTPs hides RNA base modifications. Here, we present an initial exploration of Nanopore direct RNA sequencing to assess the m6A residues in the SARS-CoV-2 sequences of ORF3a, E, M, ORF6, ORF7a, ORF7b, ORF8, N, ORF10 and the 3'-untranslated region. We identified fifteen m6A methylated positions, of which, six are in ORF N. Additionally, because m6A is associated with the DRACH motif, we compared its distribution in major SARS-CoV-2 variants. Although DRACH is highly conserved among variants, we show that variants Beta and Eta have a fourth position C > U change in DRACH at 28,884b that could affect methylation. This is the first report of direct RNA sequencing of a Brazilian SARS-CoV-2 sample coupled with the identification of modified bases.
Assuntos
Adenosina/análogos & derivados , COVID-19/virologia , Evasão da Resposta Imune/genética , RNA Viral/metabolismo , SARS-CoV-2/genética , Regiões 3' não Traduzidas , Adenosina/metabolismo , Animais , Chlorocebus aethiops , Genoma Viral , Humanos , Metilação , Sequenciamento por Nanoporos/métodos , Fases de Leitura Aberta , Análise de Sequência de RNA/métodos , Células VeroRESUMO
Appropriate control of the transcriptome is essential to regulate different aspects of gene expression during development and in response to environmental stimuli. Fast accumulating reports are recognizing and functionally characterizing several types of modifications across transcripts, which have created a new field of RNA study named epitranscriptomics. The most abundant modification found in messenger RNA (mRNA) is N6-methyladenosine (m6 A). m6 A addition is achieved by a large methyltransferase complex (MTC). The m6 A-MTC is composed of the methyltransferases METTL3 and METTL14 as the catalytic core, and several protein factors necessary for its correct catalysis, which include WTAP, RBM15, VIRMA, HAKAI, and ZC3H13. To fully appreciate the relevance of this modification, it is important to dissect the basis for the MTC function as well as to define its interaction with other cellular partners. Here, we summarize previous and recent knowledge on these issues to provide a guide for future research and put forward ideas on the flexibility and specificity of this process. This article is categorized under: RNA Processing > RNA Editing and Modification RNA Interactions with Proteins and Other Molecules > Protein-RNA Recognition.
Assuntos
Metiltransferases , Processamento Pós-Transcricional do RNA , Adenosina/metabolismo , Metiltransferases/genética , Metiltransferases/metabolismo , RNA Mensageiro/genética , RNA Mensageiro/metabolismoRESUMO
RNA plays central roles in biology and novel functions and regulation mechanisms are constantly emerging. To accomplish some of their functions within the cell, RNA molecules undergo hundreds of chemical modifications from which N6-methyladenosine (m6A), inosine (I), pseudouridine (ψ) and 5-methylcytosine (5mC) have been described in eukaryotic mRNA. Interestingly, the m6A modification was shown to be reversible, adding novel layers of regulation of gene expression through what is now recognized as epitranscriptomics. The development of molecular mapping strategies coupled to next generation sequencing allowed the identification of thousand of modified transcripts in different tissues and under different physiological conditions such as viral infections. As intracellular parasites, viruses are confronted to cellular RNA modifying enzymes and, as a consequence, viral RNA can be chemically modified at some stages of the replication cycle. This review focuses on the chemical modifications of viral RNA and the impact that these modifications have on viral gene expression and the output of infection. A special emphasis is given to m6A, which was recently shown to play important yet controversial roles in different steps of the HIV-1, HCV and ZIKV replication cycles.
Assuntos
Epigênese Genética , Transcriptoma/genética , Replicação Viral/genética , Animais , Humanos , Modelos Genéticos , Edição de RNA/genéticaRESUMO
Abstract Increased levels of homocysteine have been established as a risk factor for cardiovascular disease (CVD) by mechanisms still incompletely defined. S-Adenosylhomocysteine (SAH) is the metabolic precursor of homocysteine that accumulates in the setting of hyperhomocysteinemia and is a negative regulator of most cell methyltransferases. Several observations, summarized in the current review, support the concept that SAH, rather than homocysteine, may be the culprit in the CVD risk that has been associated with hyperhomocysteinemia. This review examines the biosynthesis and catabolism of homocysteine and how these pathways regulate accumulation of SAH. In addition, the epidemiological and experimental links between hyperhomocysteinemia and CVD are discussed, along with the evidence suggesting a role for SAH in the disease. Finally, the effects of SAH on the hypomethylation of DNA, RNA, and protein are examined, with an emphasis on how specific molecular targets may be mediators of homocysteine-associated vascular disease.