16 research outputs found
Effect of RNA secondary structure and modified bases on the inhibition of trypanosomatid protein synthesis in cell free extracts by antisense oligodeoxynucleotides.
Every messenger RNA from leishmanias and trypanosomes has at its 5' end a conserved region termed the mini-exon sequence which, however, varies from species to species. In a systematic study mRNAs from Trypanosoma brucei, Trypanosoma vivax, and Leishmania enriettii were translated in cell-free extracts in the presence of oligodeoxynucleotides complementary to part of the mini-exon sequence. The affinity of the same oligonucleotides for target and non-target mRNAs was determined by thermal elution of filter-bound complexes showing that the critical temperature of half-dissociation of the complexes was linearly related to log (l + x), where l is the length of the oligomer and x its G + C content. A few oligomers exhibited a lower Tc value than expected which was ascribed to the presence of modified RNA bases or to the existence of a hairpin structure in the L. enriettii mini-exon. In most cases the efficiency of translation inhibition by the oligonucleotides was clearly correlated to their affinity for the target RNA. The modified bases weakened the inhibition of protein synthesis by oligonucleotides complementary to these regions
Les oligonucléotides antisens : outils de génétique moléculaire et agents thérapeutiques
La fixation d’un oligonucléotide synthétique, appelé antisens, sur la séquence complémentaire d’un ARN messager choisi pour cible peut conduire à l’inhibition de la synthèse de la protéine correspondante. Il s’agit donc là d’un moyen de réguler artificiellement et de façon spécifique l’expression du gène cible. Deux mécanismes rendent compte de cet effet : d’une part un blocage physique de la progression du ribosome prévient l’initiation de la traduction, d’autre part la dégradation de l’ARNm associé à l’oligonucléotide antisens par les RNase-H empêche l’élongation de la chaîne peptidique. Des modifications chimiques peuvent être introduites dans ces molécules afin de leur conférer des propriétés particulières (résistance aux DNases, haute affinité, pénétration facilitée dans les cellules vivantes). Les oligonucléotides antisens, outils de génétique moléculaire, ont aidé à la caractérisation de la séquence mini-exon, acquise par trans-épissage, présente à l’extrémité 5' de tous les ARNm de trypanosomatidés et à celle de quelques ARNm de nématodes. De plus, des oligonucléotides antisens modifiés, complémentaires de cette séquence mini-exon induisent la mort de Trypanosoma brucei en culture; ces molécules pourraient donc constituer des prototypes d’une nouvelle classe d’agents thérapeutiques
More at stake in stem-cell patents
Austin Smith and others argue in
favour of patenting technologies
derived from human embryonic
stem cells (Nature 472, 418;
2011), a case still pending with
the European Court of Justice.
But there is more at stake than
European commercial interests.
In 1998, agreement was
reached in Europe under
Directive 98/44 not to recognize
patents involving the use of
human embryos for commercial
purposes (R. Hipp and P. Liese
Nature 474, 36; 2011).
The court must decide
whether the use of these cells
\u2018necessitates the prior destruction
of human embryos or their use
as base material\u2019, as the advocategeneral,
Yves Bot, has argued
(see go.nature.com/gsap8n).
If so, such use would seem to
fall beyond the scope of what is
legally patentable.
Smith et al. warn that
\u201cEuropean discoveries could
be translated into applications
elsewhere, at a potential cost
to the European citizen.\u201d This
begs the question of whether
patents, which may also be held
by non-European companies,
may sometimes impede wider
research cooperation (S. Rabin
Nature Biotechnol. 23, 817\u2013819;
2005).
In any case there will often
be some commercial risk
whenever Europe defends a
more rigorous ethical standard
than is defended elsewhere. This
risk is not itself an argument
against upholding the standard
prescribed by law.
Without prejudice to the
final judgment in this case, the
resolution of patent law is and
ought to be more than a question
of European commercial interest