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M Picard-Bennoun

Publications and source records attributed to M Picard-Bennoun.

9 recordsLinked to original sources
PubMed1986

At least seven ribosomal proteins are involved in the control of translational accuracy in a eukaryotic organism.

In the filamentous fungus Podospora anserina, ribosomal proteins of 60 mutants impaired in the control of translational fidelity have been submitted to electrophoretic analysis. The "four corners" system combining four different two-dimensional polyacrylamide gel electrophoretic systems has been used. An altered electrophoretic pattern has been observed for 12 mutants. In mutants su3, su12 and su11 (decreased translational fidelity), proteins S1, S7 and S8, respectively, are altered. For AS mutants (increased translational fidelity), proteins S9, S12 and S19, respectively, are altered in AS9, AS1 and AS6 mutants, and protein S29 is lacking in AS3 mutants. The data suggest that five of these genes (at least) are the structural genes for the relevant proteins (su3:S1, su12:S7, AS1:S12, AS6:S19, AS9:S9), while the AS3 gene may code for a modifying enzyme.

Electrophoresis, Polyacrylamide Gel↗
PubMed1985

Introns, protein syntheses and aging.

In the fungus Podospora, a correlation has recently been established between the presence of circular DNA molecules arising from the mitochondrial genome (SEN-DNAs) and the senescence syndrome. Here, I propose a hypothesis which accounts for the initial event which leads to the first SEN-DNA. A molecule in the most frequent situation where the SEN-DNA is an intron which might code for a maturase. This hypothesis is based upon several observations made either in Podospora or in the yeast S. cerevisiae. It assumes that mitochondrially synthesized maturases are unspecific nucleases able to work at the level of RNA and DNA molecules. Their specificity for RNA splicing instead of DNA is given by cytoplasmic proteins. Therefore, if the balance between cytoplasmic and mitochondrial protein syntheses is disturbed in favour of the mitochondrial compartment, the maturase would be accumulated and allowed to splice introns from DNA instead of RNA molecules. This hypothesis can account for aging of higher eucaryotic cells by postulating analogous processes in their nuclear compartment.

Ascomycota↗
PubMed1982

Does translational ambiguity increase during cell differentiation?

Several observations made in the fungus Podospora anserina suggest that translational ambiguity may increase, and possibly must increase, at specific stages of the life cycle. Such changes in the properties of the translational apparatus seem to occur as well in the yeast S. cerevisiae and in the alga C. reinhardii. A slight increase of the misreading level would allow readthrough or frameshifting necessary to synthesise regulatory proteins in low amount at key points of cellular differentiation.

Ascomycota↗
PubMed1982

Analysis of revertants of a ribosomal mutation in Podospora anserina: evidence for new ribosomal mutations which confer hypersensitivity to paromomycin.

This paper describes the analysis of cold-resistant revertants of a cold-sensitive mutant. Pm1-1 is a ribosomal mutation screened for its paromomycin resistance. Suppression of its cold sensitivity occurs with two kinds of external mutations localized in two different loci. One of them, PmB, is assumed to be a ribosomal gene. PmB mutations confer hypersensitivity to paromomycin in vivo as well as in vitro in a cell-free protein synthesis system.

Ascomycota↗
PubMed1981

Mutations affecting translational fidelity in the eucaryote Podospora anserina: characterization of two ribosomal restrictive mutations.

Fifty-nine mutations that restrict suppressor efficiency were selected in the fungus Podospora anserina using four different screening methods. Previous genetic analysis has shown that these antisuppressors lie in six loci and that they could be similar to ribosomal restrictive mutations known in Escherichia coli. The present study deals with the response of two of them, AS1-1 and AS6-1, to paromomycin and low temperature both in vivo and in vitro. The data demonstrate that ribosomes of the mutant and double-mutant strains are equally resistant to the ambiguity effect of paromomycin. These data are the first demonstration of mutations that increase translational fidelity in eucaryotic organism.

Ascomycota↗
PubMed1980

Search for ribosomal mutants in Podospora anserina: genetic analysis of mutants resistant to paromomycin.

It has recently been shown that paromomycin, an antibiotic of the aminoglycoside family, is also active on eukaryotic cytoplasmic ribosomes. In the fungus Podospora anserina, genetic analysis of ten mutants resistant to high doses of paromomycin shows that this resistance is caused by mutations in two different nuclear genes. These mutants display pleiotropic phenotypes (cold sensitivity, mycelium and spore appearance and coloration, cross-resistance to other antibiotics). Double mutants are either lethal or very altered and unstable. Moreover, the cytochrome spectra of these mutants seem to indicate that cytoplasmic protein synthesis is affected. The mutants also display a slight suppressor effect. We can therefore assume that these mutations affect cytoplasmic ribosomes.

Ascomycota↗
PubMed1976

Genetic evidence of ribosomal antisuppressors in Podospora anserina.

Antisuppressors were screened for with the help of informational suppressors in Podospores anserina. Four mutations in the AS1 locus and two in the AS2 locus were isolated, using allele non specific suppressors supposed to be ribosomal ambiguity mutations. Four mutations in the AS3 locus and 45 in the AS4 locus were obtained, using a nonsense (t-RNA like) suppressor. All antisuppressors are partially dominant. Most mutations in the AS4 locus are lethal. The four mutants at the AS3 locus and 6 out of the 8 viable mutants at the AS4 locus are cold sensitive. Phenotypic properties and action spectra of the antisuppressors suggest that they are restrictive ribosomal mutations.

Ascomycota↗