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P Deschênes

Publications and source records attributed to P Deschênes.

6 recordsLinked to original sources
PubMed2000

The database of the smallest known auto-replicable RNA species: viroids and viroid-like RNAs.

This is an online database in order to facilitate research on viroid, viroid-like RNAs and human hepatitis delta virus by presenting a large number of sequences and related data in a comprehensive and user-friendly format (e.g., position of their self-catalytic domains, open reading frame, prediction of the most stable secondary structures, etc.). This online database is available on the WWW at http://www.callisto.si. usherb.ca/jpperra

Catalysis↗
PubMed2000

Nucleotides -1 to -4 of hepatitis delta ribozyme substrate increase the specificity of ribozyme cleavage.

In the past, the use of delta ribozyme as a therapeutic tool was limited because substrate specificity was thought to be determined by only 8 nucleotides. Recently, we have accumulated evidence suggesting that the substrate sequence upstream of the cleavage site, which is not involved in the binding with the delta ribozyme, appears to be essential in the selection of an appropriate cleavage site. To understand the role of this region in efficient cleavage, we synthesized a collection of small substrates that possessed single and multiple mutations in positions -1 to -4 and determined the kinetic parameters of their cleavage using a model antigenomic delta ribozyme. Some substrates were found to be uncleavage, whereas others showed >60-fold difference in relative specificity between the least and most efficiently cleaved substrates. The base at each position from -1 to -4 contributes differently to the ability of a substrate to be cleaved. An optimal sequence for positions -1 to -4 was determined to be -1HRHY(-4) (H = U, C, or A). These results shed light on new features that contribute to the substrate requirement of delta ribozyme cleavage and should increase interest in the use of this unique ribozyme.

Base Sequence↗
PubMed1999

The viroid and viroid-like RNA database.

This is an online database to facilitate research on viroid, viroid-like RNAs and human hepatitis delta virus (vHDV) by presenting a large number of sequences and related data in a comprehensive and user-friendly format (e.g. position of their self-catalytic domains, open reading frame of the vHDV, prediction of the most stable secondary structures, etc.). Most of these RNA species share a common proposed replication pattern known as a DNA-independent rolling circle mechanism. Together, these species form the 'brotherhood' of the smallest known auto-replicable RNAs. This online database is available on the World Wide Web at http://www.callisto.si.usherb.ca/jpperra

Databases, Factual↗
PubMed1998

The sensitivity of the human Kv1.3 (hKv1.3) lymphocyte K+ channel to regulation by PKA and PKC is partially lost in HEK 293 host cells.

cDNA encoding the full-length hKv1.3 lymphocyte channel and a C-terminal truncated (delta 459-523) form that lacks the putative PKA Ser468 phosphorylation site were stably transfected in human embryonic kidney (HEK) 293 cells. Immunostaining of the transfected cells revealed a distribution at the plasma membrane that was uniform in the case of the full-length channel whereas clustering was observed in the case of the truncated channel. Some straining within the cell cytoplasm was found in both instances, suggesting an active process of biosynthesis. Analyses of the K+ current by the patch-clamp technique in the whole cell configuration showed that depolarizing steps to 40 mV from a holding potential (HP) of -80 mV elicited an outward current of 2 to 10 nA. The current threshold was positive to -40 mV and the current amplitude increased in a voltage-dependent manner. The parameters of activation were -5.7 and -9.9 mV (slope factor) and -35 mV (half activation, V0.5) in the case of the full-length and truncated channels, respectively. The characteristics of the inactivation were 14.2 and 24.6 mV (slope factor) and -17.3 and -39.0 mV (V0.5) for the full-length and truncated channels, respectively. The activation time constant of the full-length channel for potentials ranging from -30 to 40 mV decreased from 18 to 12 msec whereas the inactivation time constant decreased from 6600 msec at -30 mV to 1800 msec at 40 mV. The unit current amplitude measured in cells bathing in 140 mM KCl was 1.3 +/- 0.1 pA at 40 mV, the unit conductance, 34.5 pS and the zero current voltage, 0 mV. Both forms of the channels were inhibited by TEA, 4-AP, Ni2+ and charybdotoxin. In contrast to the native (Jurkat) lymphocyte Kv1.3 channel that is fully inhibited by PKA and PKC, the addition of TPA resulted in 34.6 +/- 7.3% and 38.7 +/- 9.4% inhibition of the full-length and the truncated channels, respectively, 8-BrcAMP induced a 39.4 +/- 5.4% inhibition of the full-length channel but had no effect (8.6 +/- 8.3%) on the truncated channel. Cell dialysis with alkaline phosphatase had no effects, suggesting that the decreased sensitivity of the transfected channels to PKA and PKC was not due to an already phosphorylated channel. Patch extract experiments suggested that the hKv1.3 channel was partially sensitive to PKA and PKC. Cotransfecting the Kv beta 1.2 subunit resulted in a decrease in the value of the time constant of inactivation of the full-length channel but did not modify its sensitivity to PKA and PKC. The cotransfected Kv beta 2 subunit had no effects. Our results indicate that the hKv1.3 lymphocyte channel retains its electrophysiological characteristics when transfected in the Kv beta-negative HEK 293 cell line but its sensitivity to modulation by PKA and PKC is significantly reduced.

Cell Line↗