ARN non codant

Résumé

Un ARN non codant (ou ARNnm pour ARN non messager) est un ARN, issu de la transcription de l'ADN, qui ne sera pas traduit en protéine par les ribosomes. L'importance quantitative et fonctionnelle des ARN non codants a été longtemps sous estimée. On en connaît aujourd'hui une grande diversité, et il semblerait qu'une partie importante des génomes soit transcrite en ARN, alors que, dans le génome humain par exemple, seulement 1,2 % de l'information de l'ADN est traduite en protéines. Différents types d'ARN non codant

Les ARN ribosomiques sont des ARN formant les ribosomes, associés à des protéines. Chez les eucaryotes, par exemple, on distingue les ARNr 5S, 5.8S, 18S et 28S.
Les ARN de transfert sont des ARN intervenant dans la traduction, qui associent spécifiquement à un codon de trois nucléotides un acide aminé déterminé par le code génétique.
Les introns sont les parties d'un gène qui sont excisées lors de l'épissage de l'ARNm précédant la traduction chez les eu

Source officielle

https://fr.wikipedia.org/wiki/ARN_non_codant

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A high-content RNAi screen reveals multiple roles for long noncoding RNAs in cell division

Christina Ernst

Genome stability relies on proper coordination of mitosis and cytokinesis, where dynamic microtubules capture and faithfully segregate chromosomes into daughter cells. With a high-content RNAi imaging screen targeting more than 2,000 human lncRNAs, we identify numerous lncRNAs involved in key steps of cell division such as chromosome segregation, mitotic duration and cytokinesis. Here, we provide evidence that the chromatin-associated lncRNA, linc00899, leads to robust mitotic delay upon its depletion in multiple cell types. We perform transcriptome analysis of linc00899-depleted cells and identify the neuronal microtubule-binding protein, TPPP/p25, as a target of linc00899. We further show that linc00899 binds TPPP/p25 and suppresses its transcription. In cells depleted of linc00899, upregulation of TPPP/p25 alters microtubule dynamics and delays mitosis. Overall, our comprehensive screen uncovers several lncRNAs involved in genome stability and reveals a lncRNA that controls microtubule behaviour with functional implications beyond cell division.

2020

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We present and validate BlastR, a method for efficiently and accurately searching non-coding RNAs. Our approach relies on the comparison of di-nucleotides using BlosumR, a new log-odd substitution matrix. In order to use BlosumR for comparison, we recoded RNA sequences into protein-like sequences. We then showed that BlosumR can be used along with the BlastP algorithm in order to search non-coding RNA sequences. Using Rfam as a gold standard, we benchmarked this approach and show BlastR to be more sensitive than BlastN. We also show that BlastR is both faster and more sensitive than BlastP used with a single nucleotide log-odd substitution matrix. BlastR, when used in combination with WU-BlastP, is about 5% more accurate than WU-BlastN and about 50 times slower. The approach shown here is equally effective when combined with the NCBI-Blast package. The software is an open source freeware available from www.tcoffee.org/blastr.html.

Oxford University Press2011

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Only a very small fraction of long noncoding RNAs (lncRNAs) are well characterized. The evolutionary history of lncRNAs can provide insights into their functionality, but the absence of lncRNA annotations in non-model organisms has precluded comparative analyses. Here we present a large-scale evolutionary study of lncRNA repertoires and expression patterns, in 11 tetrapod species. We identify approximately 11,000 primate-specific lncRNAs and 2,500 highly conserved lncRNAs, including approximately 400 genes that are likely to have originated more than 300 million years ago. We find that lncRNAs, in particular ancient ones, are in general actively regulated and may function predominantly in embryonic development. Most lncRNAs evolve rapidly in terms of sequence and expression levels, but tissue specificities are often conserved. We compared expression patterns of homologous lncRNA and protein-coding families across tetrapods to reconstruct an evolutionarily conserved co-expression network. This network suggests potential functions for lncRNAs in fundamental processes such as spermatogenesis and synaptic transmission, but also in more specific mechanisms such as placenta development through microRNA production.

Nature Publishing Group2014

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