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Maurille J Fournier

Publications and source records attributed to Maurille J Fournier.

5 recordsLinked to original sources
PubMed2003

Ribosome structure and activity are altered in cells lacking snoRNPs that form pseudouridines in the peptidyl transferase center.

One of the oldest questions in RNA science is the role of nucleotide modification. Here, the importance of pseudouridine formation (Psi) in the peptidyl transferase center of rRNA was examined by depleting yeast cells of 1-5 snoRNAs that guide a total of six Psi modifications. Translation was impaired substantially with loss of a conserved Psi in the A site of tRNA binding. Depletion of other Psis had subtle or no apparent effect on activity; however, synergistic effects were observed in some combinations. Pseudouridines are proposed to enhance ribosome activity by altering rRNA folding and interactions, with some Psis having greater effects than others. The possibility that modifying snoRNPs might affect ribosome structure in other ways is also discussed.

Base Sequence↗
PubMed2003

RNA-modifying machines in archaea.

It has been known for nearly half a century that coding and non-coding RNAs (mRNA, and tRNAs and rRNAs respectively) play critical roles in the process of information transfer from DNA to protein. What is both surprising and exciting, are the discoveries in the last decade that cells, particularly eukaryotic cells, contain a plethora of non-coding RNAs and that these RNAs can either possess catalytic activity or can function as integral components of dynamic ribonucleoprotein machines. These machines appear to mediate diverse, complex and essential processes such as intron excision, RNA modification and editing, protein targeting, DNA packaging, etc. Archaea have been shown to possess RNP complexes; some of these are authentic homologues of the eukaryotic complexes that function as machines in the processing, modification and assembly of rRNA into ribosomal subunits. Deciphering how these RNA-containing machines function will require a dissection and analysis of the component parts, an understanding of how the parts fit together and an ability to reassemble the parts into complexes that can function in vitro. This article summarizes our current knowledge about small-non-coding RNAs in Archaea, their roles in ribosome biogenesis and their relationships to the complexes that have been identified in eukaryotic cells.

Amino Acid Sequence↗
PubMed2002

rRNA modifications and ribosome function.

The development of three-dimensional maps of the modified nucleotides in the ribosomes of Escherichia coli and yeast has revealed that most (approximately 95% in E. coli and 60% in yeast) occur in functionally important regions. These include the peptidyl transferase centre, the A, P and E sites of tRNA- and mRNA binding, the polypeptide exit tunnel, and sites of subunit-subunit interaction. The correlations suggest that many ribosome functions benefit from nucleotide modification.

Binding Sites↗
PubMed2002

Depletion of free 30S ribosomal subunits in Escherichia coli by expression of RNA containing Shine-Dalgarno-like sequences.

We have constructed synthetic coding sequences for the expression of poly(alpha,L-glutamic acid) (PLGA) as fusion proteins with dihydrofolate reductase (DHFR) in Escherichia coli. These PLGA coding sequences use both GAA and GAG codons for glutamic acid and contain sequence elements (5'-GAGGAGG-3') that resemble the consensus Shine-Dalgarno (SD) sequence found at translation initiation sites in bacterial mRNAs. An unusual feature of DHFR-PLGA expression is that accumulation of the protein is inversely related to the level of induction of its mRNA. Cellular protein synthesis was inhibited >95% by induction of constructs for either translatable or untranslatable PLGA RNAs. Induction of PLGA RNA resulted in the depletion of free 30S ribosomal subunits and the appearance of new complexes in the polyribosome region of the gradient. Unlike normal polyribosomes, these complexes were resistant to breakdown in the presence of puromycin. The novel complexes contained 16S rRNA, 23S rRNA, and PLGA RNA. We conclude that multiple noninitiator SD-like sequences in the PLGA RNA inhibit cellular protein synthesis by sequestering 30S small ribosomal subunits and 70S ribosomes in nonfunctional complexes on the PLGA mRNA.

Base Sequence↗