363 research outputs found
RNA G-quadruplexes and their potential regulatory roles in translation
Abstract: DNA guanine (G)-rich 4-stranded helical nucleic acid structures called G-quadruplexes (G4), have been extensively studied during the last decades. However, emerging evidence reveals that 50- and
30-untranslated regions (50- and 30-UTRs) as well as open reading frames (ORFs) contain putative
RNA G-quadruplexes. These stable secondary structures play key roles in telomere homeostasis and
RNA metabolism including pre-mRNA splicing, polyadenylation, mRNA targeting and translation.
Interestingly, multiple RNA binding proteins such as nucleolin, FMRP, DHX36, and Aven were
identified to bind RNA G-quadruplexes. Moreover, accumulating reports suggest that RNA
G-quadruplexes regulate translation in cap-dependent and -independent manner. Herein, we
discuss potential roles of RNA G-quadruplexes and associated trans-acting factors in the regulation
of mRNA translation
Road User Detection in Videos
Successive frames of a video are highly redundant, and the most popular
object detection methods do not take advantage of this fact. Using multiple
consecutive frames can improve detection of small objects or difficult examples
and can improve speed and detection consistency in a video sequence, for
instance by interpolating features between frames. In this work, a novel
approach is introduced to perform online video object detection using two
consecutive frames of video sequences involving road users. Two new models,
RetinaNet-Double and RetinaNet-Flow, are proposed, based respectively on the
concatenation of a target frame with a preceding frame, and the concatenation
of the optical flow with the target frame. The models are trained and evaluated
on three public datasets. Experiments show that using a preceding frame
improves performance over single frame detectors, but using explicit optical
flow usually does not
Road User Detection in Videos
Successive frames of a video are highly redundant, and the most popular
object detection methods do not take advantage of this fact. Using multiple
consecutive frames can improve detection of small objects or difficult examples
and can improve speed and detection consistency in a video sequence, for
instance by interpolating features between frames. In this work, a novel
approach is introduced to perform online video object detection using two
consecutive frames of video sequences involving road users. Two new models,
RetinaNet-Double and RetinaNet-Flow, are proposed, based respectively on the
concatenation of a target frame with a preceding frame, and the concatenation
of the optical flow with the target frame. The models are trained and evaluated
on three public datasets. Experiments show that using a preceding frame
improves performance over single frame detectors, but using explicit optical
flow usually does not
A conserved target site in HIV-1 Gag RNA is accessible to inhibition by both an HDV ribozyme and a short hairpin RNA
Abstract: Antisense-based molecules targeting HIV-1 RNA have the potential to be used as part of gene or drug therapy to treat HIV-1
infection. In this study, HIV-1 RNA was screened to identify more conserved and accessible target sites for ribozymes based on
the hepatitis delta virus motif. Using a quantitative screen for effects on HIV-1 production, we identified a ribozyme targeting
a highly conserved site in the Gag coding sequence with improved inhibitory potential compared to our previously described
candidates targeting the overlapping Tat/Rev coding sequence. We also demonstrate that this target site is highly accessible
to short hairpin directed RNA interference, suggesting that it may be available for the binding of antisense RNAs with different
modes of action. We provide evidence that this target site is structurally conserved in diverse viral strains and that it is
sufficiently different from the human transcriptome to limit off-target effects from antisense therapies. We also show that the
modified hepatitis delta virus ribozyme is more sensitive to a mismatch in its target site compared to the short hairpin RNA.
Overall, our results validate the potential of a new target site in HIV-1 RNA to be used for the development of antisense therapies
Exploring mRNA 3'-UTR G-quadruplexes: evidence of roles in both alternative polyadenylation and mRNA shortening
Abstract: Guanine-rich RNA sequences can fold into noncanonical,
four stranded helical structures called
G-quadruplexes that have been shown to be widely
distributed within the mammalian transcriptome,
as well as being key regulatory elements in various
biological mechanisms. That said, their role
within the 30-untranslated region (UTR) of mRNA
remains to be elucidated and appreciated.
A bioinformatic analysis of the 30-UTRs of mRNAs
revealed enrichment in G-quadruplexes. To shed
light on the role(s) of these structures, those
found in the LRP5 and FXR1 genes were
characterized both in vitro and in cellulo. The 30-
UTR G-quadruplexes were found to increase
the efficiencies of alternative polyadenylation sites,
leading to the expression of shorter transcripts
and to possess the ability to interfere with the
miRNA regulatory network of a specific mRNA.
Clearly, G-quadruplexes located in the 30-UTRs of
mRNAs are cis-regulatory elements that have a
significant impact on gene expression
Target-dependent on/off switch increases ribozyme fidelity
Ribozymes, RNA molecules that catalyze the cleavage of RNA substrates, provide an interesting alternative to the RNA interference (RNAi) approach to gene inactivation, especially given the fact that RNAi seems to trigger an immunological response. Unfortunately, the limited substrate specificity of ribozymes is considered to be a significant hurdle in their development as molecular tools. Here, we report the molecular engineering of a ribozyme possessing a new biosensor module that switches the cleavage activity from ‘off’ (a ‘safety lock’) to ‘on’ solely in the presence of the appropriate RNA target substrate. Both proof-of-concept and the mechanism of action of this man-made riboswitch are demonstrated using hepatitis delta virus ribozymes that cleave RNA transcripts derived from the hepatitis B and C viruses. To our knowledge, this is the first report of a ribozyme bearing a target-dependent module that is activated by its RNA substrate, an arrangement which greatly diminishes non-specific effects. This new approach provides a highly specific and improved tool with significant potential for application in the fields of both functional genomics and gene therapy
Structurexplor : a platform for the exploration of structural features of RNA secondary structures
Abstract : Summary: Discovering function-related structural features, such as the cloverleaf shape of transfer
RNA secondary structures, is essential to understand RNA function. With this aim, we have developed
a platform, named Structurexplor, to facilitate the exploration of structural features in
populations of RNA secondary structures. It has been designed and developed to help biologists
interactively search for, evaluate and select interesting structural features that can potentially explain
RNA functions
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