15 research outputs found
Competitive and Cooperative Interactions Mediate RNA Transfer from Herpesvirus Saimiri ORF57 to the Mammalian Export Adaptor ALYREF
The essential herpesvirus adaptor protein HVS ORF57, which has homologs in all other herpesviruses, promotes viral mRNA
export by utilizing the cellular mRNA export machinery. ORF57 protein specifically recognizes viral mRNA transcripts, and
binds to proteins of the cellular transcription-export (TREX) complex, in particular ALYREF. This interaction introduces viral
mRNA to the NXF1 pathway, subsequently directing it to the nuclear pore for export to the cytoplasm. Here we have used a
range of techniques to reveal the sites for direct contact between RNA and ORF57 in the absence and presence of ALYREF. A
binding site within ORF57 was characterized which recognizes specific viral mRNA motifs. When ALYREF is present, part of
this ORF57 RNA binding site, composed of an a-helix, binds preferentially to ALYREF. This competitively displaces viral RNA
from the a-helix, but contact with RNA is still maintained by a flanking region. At the same time, the flexible N-terminal
domain of ALYREF comes into contact with the viral RNA, which becomes engaged in an extensive network of synergistic
interactions with both ALYREF and ORF57. Transfer of RNA to ALYREF in the ternary complex, and involvement of individual
ORF57 residues in RNA recognition, were confirmed by UV cross-linking and mutagenesis. The atomic-resolution structure
of the ORF57-ALYREF interface was determined, which noticeably differed from the homologous ICP27-ALYREF structure.
Together, the data provides the first site-specific description of how viral mRNA is locked by a herpes viral adaptor protein in
complex with cellular ALYREF, giving herpesvirus access to the cellular mRNA export machinery. The NMR strategy used
may be more generally applicable to the study of fuzzy protein-protein-RNA complexes which involve flexible polypeptide
regions
Effects of temperature in juvenile seabass (Dicentrarchus labrax L.) biomarker responses and behaviour: implications for environmental monitoring
The effects of temperature on European seabass
(Dicentrarchus labrax L.) juveniles were investigated using
a 30-day bioassay carried out at 18 and 25 °C in laboratory
conditions. A multiparameter approach was applied including
fish swimming velocity and several biochemical parameters
involved in important physiological functions. Fish exposed for
four weeks to 25 °C showed a decreased swimming capacity,
concomitant with increased oxidative stress (increased catalase
and glutathione peroxidase activities) and damage (increased
lipid peroxidation levels), increased activity of an enzyme
involved in energy production through the aerobic pathway
(isocitrate dehydrogenase) and increased activities of brain and
muscle cholinesterases (neurotransmission) compared to fish
kept at 18 °C. Globally, these findings indicate that basic
functions, essential for juvenile seabass surviving and well
performing in the wild, such as predation, predator avoidance,
neurofunction and ability to face chemical stress may be compromised
with increasing water temperature. This may be of
particular concern if D. labrax recruitment phase in northwest
European estuaries and coastal areas happens gradually inmore
warm environments as a consequence of global warming.
Considering that the selected endpoints are generally applied
in monitoring studies with different species, these findings also
highlight the need of more research, including interdisciplinary
and multiparameter approaches, on the impacts of temperature
on marine species, and stress the importance of considering
scenarios of temperature increase in environmental monitoring
and in marine ecological risk assessment