ADN ARNm

[invite7825c20b]

laisse un moi un peu de temps je te retrouves la publi où ils avaient montrés l'auto épissage in vitro (Bonen je crois mais je suis pas sur).
Et pour les homing endonucléase codées par la boucle 4, elle a souvent souvent été considérée comme une "maturase", c'est à dire que c'est elle qui permettrait en partie l'activité d'épissage. Mais il me semble qu'aucune preuve n'a été apportée. D'autant plus que nous au labo on travaille un peu sur les groupes II des mitos de plantes et dans beaucoup de cas l'ORF intronique a disparu ou est dégéné et ne code plus pour une protéine "correcte".
Je disais pas que in vivo les conditions salines étaient dures, juste que celles employées par le in vitro n'étaient pas compatibles avec du in vivo.
Je lance une centri et je cherche
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[invite7825c20b]

c'est encore moi. Je met l'abstract d'une review qui fait le point sur les introns de groupe II. Elle est longue mais elle fait le tour de la question et la biblio reprend tout. Pour Bonen désolé je me suis planté c'était pas lui (lui c'est le trans splicing).

Critical Reviews in Biochemistry and Molecular Biology, 38(3):249–303 (2003)

Group II Introns: Structure and Catalytic Versatility of Large Natural Ribozymes Karola Lehmann and Udo Schmidt
ABSTRACT: Group II introns are large, natural catalytic RNAs or ribozymes that were discovered in organelles of certain protists, fungi, algae, and plants and more recently also in prokaryotic organisms. In vitro, some members were found to self-splice from their pre-RNAs by two consecutive transesterification reactions joining the flanking exons and releasing the intron in a typical lariat form. Apart from self-splicing, a variety of other in vitro activities have been detected for group II introns demonstrating their amazing catalytic versatility. Group II introns fold into a conserved secondary structure consisting of six domains radiating from a central wheel that brings the 5' and 3' splice junction into close proximity. Domain 1 is the largest domain that is assumed to deliver the molecular scaffold assembling the intron in its active structure, while domain 5 is the phylogenetically most conserved part that represents the active site of the ribozyme. In vivo, the splicing reaction of many, if not all group II introns is assisted by proteins either encoded by the introns themselves (maturases), or encoded by other genes of the host organisms. The host proteins known to date have additional cellular functions and seem to have been adapted for splicing during evolution. Some of the protein-encoding group II introns were also shown to act as mobile genetic elements. They can integrate efficiently into intronless alleles of the same gene (homing) and at much lower frequencies into ectopic sites (transposition). The mobility process depends on intron encoded protein functions (endonuclease and reverse transcriptase) and on the intron RNA. This review provides a comprehensive survey of the structure/function relationships and the reaction potential of group II introns, the structurally most complicated, but also most fascinating ribozymes when looking at their catalytic repertoire in vitro and in vivo.