ARN long non-codant

Un ARN long non-codant (ARNlnc) est généralement défini comme étant un transcrit d'une longueur supérieure ou égale à 200 nucléotides et qui ne code pas une protéine, ou plus précisément, qui n'a pas de cadre de lecture ouvert comparable à celui d'un ARN messager. Les ARNlnc constituent la plus vaste classe de gènes chez les mammifères, mais sont encore très mal connus. Les fonctions biologiques des ARNlnc sont mal connues, mais ces transcrits (et donc les gènes qui les codent) semblent être des régulateurs de l'expression d'autres gènes, et sont impliqués dans de nombreux processus biologiques et maladies. La transcription d'une partie des ARNlnc est assurée par l'ARN polymérase II, comme pour les ARN messagers. Les transcrits produits subissent l'épissage et reçoivent une coiffe et une queue dite « poly-A ». Le niveau d'expression des ARNlnc (c'est-à-dire la quantité de transcrits produits) est inférieure à celle des ARN messagers, d'un facteur 10 environ. De plus, l'expression de

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Human genome

The human genome is a complete set of nucleic acid sequences for humans, encoded as DNA within the 23 chromosome pairs in cell nuclei and in a small DNA molecule found within individual mitochondria.

ARN non codant

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

Acide ribonucléique

vignette|Structure tridimensionnelle d'un ARN régulateur (riboswitch). vignette|Structure moléculaire de l'ARN. L'acide ribonucléique ou ARN (en anglais, RNA, pour ribonucleic acid) est un acide nuc

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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The evolution of lncRNA repertoires and expression patterns in tetrapods

Anamaria Necsulea, Magali Soumillon

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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Assessing Recent Selection and Functionality at Long Noncoding RNA Loci in the Mouse Genome

Anamaria Necsulea

Long noncoding RNAs (lncRNAs) are one of the most intensively studied groups of noncoding elements. Debate continues over what proportion of lncRNAs are functional or merely represent transcriptional noise. Although characterization of individual lncRNAs has identified approximately 200 functional loci across the Eukarya, general surveys have found only modest or no evidence of long-term evolutionary conservation. Although this lack of conservation suggests that most lncRNAs are nonfunctional, the possibility remains that some represent recent evolutionary innovations. We examine recent selection pressures acting on lncRNAs in mouse populations. We compare patterns of within-species nucleotide variation at approximately 10,000 lncRNA loci in a cohort of the wild house mouse, Mus musculus castaneus, with between-species nucleotide divergence from the rat (Rattus norvegicus). Loci under selective constraint are expected to show reduced nucleotide diversity and divergence. We find limited evidence of sequence conservation compared with putatively neutrally evolving ancestral repeats (ARs). Comparisons of sequence diversity and divergence between ARs, protein-coding (PC) exons and lncRNAs, and the associated flanking regions, show weak, but significantly lower levels of sequence diversity and divergence at lncRNAs compared with ARs. lncRNAs conserved deep in the vertebrate phylogeny show lower within species sequence diversity than lncRNAs in general. A set of 74 functionally characterized lncRNAs show levels of diversity and divergence comparable to PC exons, suggesting that these lncRNAs are under substantial selective constraints. Our results suggest that, in mouse populations, most lncRNA loci evolve at rates similar to ARs, whereas older lncRNAs tend to show signals of selection similar to PC genes.

Oxford Univ Press2015

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BIO-205: Cellular and molecular biology I

The course covers the regulation of gene expression, which translates the information contained in the genome into function, by adjusting the levels and activities of mRNAs and proteins to the needs of specific cells, tissues and environments. A particular emphasis is given on experimental methods.

BIO-105: Cellular biology and biochemistry for engineers

Basic course in biochemistry as well as cellular and molecular biology for non-life science students enrolling at the Master or PhD thesis level from various engineering disciplines. It reviews essential notions necessary for a training in biology-related engineering fields.