2 research outputs found
The bent conformation of poly(A)-binding protein induced by RNA-binding is required for its translational activation function
<p>A recent study revealed that poly(A)-binding protein (PABP) bound to poly(A) RNA exhibits a sharply bent configuration at the linker region between RNA-recognition motif 2 (RRM2) and RRM3, whereas free PABP exhibits a highly flexible linear configuration. However, the physiological role of the bent structure of mRNA-bound PABP remains unknown. We investigated a role of the bent structure of PABP by constructing a PABP variant that fails to form the poly(A)-dependent bent structure but maintains its poly(A)-binding activity. We found that the bent structure of PABP/poly(A) complex is required for PABP's efficient interaction with eIF4G and eIF4G/eIF4E complex. Moreover, the mutant PABP had compromised translation activation function and failed to augment the formation of 80S translation initiation complex in an <i>in vitro</i> translation system. These results suggest that the bent conformation of PABP, which is induced by the interaction with 3′ poly(A) tail, mediates poly(A)-dependent translation by facilitating the interaction with eIF4G and the eIF4G/eIF4E complex. The preferential binding of the eIF4G/eIF4E complex to the bent PABP/poly(A) complex seems to be a mechanism discriminating the mRNA-bound PABPs participating in translation from the idling mRNA-unbound PABPs.</p
Light-Induced Fluorescence Modulation of Quantum Dot-Crystal Violet Conjugates: Stochastic Off–On–Off Cycles for Multicolor Patterning and Super-Resolution
Photoswitching
or modulation of quantum dots (QDs) can be promising
for many fields that include display, memory, and super-resolution
imaging. However, such modulations have mostly relied on photomodulations
of conjugated molecules in QD vicinity, which typically require high
power of high energy photons at UV. We report a visible light-induced
facile modulation route for QD-dye conjugates. QD crystal violets
conjugates (QD-CVs) were prepared and the crystal violet (CV) molecules
on QD quenched the fluorescence efficiently. The fluorescence of QD-CVs
showed a single cycle of emission burst as they go through three stages
of (i) initially quenched “off” to (ii) photoactivated
“on” as the result of chemical change of CVs induced
by photoelectrons from QD and (iii) back to photodarkened “off”
by radical-associated reactions. Multicolor on-demand photopatterning
was demonstrated using QD-CV solid films. QD-CVs were introduced into
cells, and excitation with visible light yielded photomodulation from
“off” to “on” and “off”
by nearly ten fold. Individual photoluminescence dynamics of QD-CVs
was investigated using fluorescence correlation spectroscopy and single
QD emission analysis, which revealed temporally stochastic photoactivations
and photodarkenings. Exploiting the stochastic fluorescence burst
of QD-CVs, simultaneous multicolor super-resolution localizations
were demonstrated