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Bernard Dujon
Bernard Dujon is a French geneticist, born on August 8, 1947, in Meudon (Hauts-de-Seine). He is Professor Emeritus at Sorbonne University and the Institut Pasteur since 2015. He is a member of the French Academy of sciences.
Bernard Dujon grew up as a teenager in the Paris suburban area and went to school at Maisons-Lafitte, where his parents settled in 1958. He became interested in biology very early and at the age of eleven started collecting biological material from his natural environment, plants, fossils, insects, shells, etc. He became in 1965 a laureate of the Concours Général, a nation-wide yearly contest, at the same time he was obtaining his baccalauréat. He started a degree of biology at the Faculté des Sciences de Paris the same year. He graduated in the top 1% of students and was offered the opportunity to compete for an oral exam at the prestigious Ecole Normale Supérieure (ENS rue d'Ulm), was ranked first and admitted there the following year (1966). He therefore became a normalien at the early age of 19, when most of the students attracted by this career are still preparing in specialized schools for this written and oral competition. There, he attended lectures at the Faculté de Sciences for two years, before choosing Genetics as a specialization during his third year. After a master's degree in Genetics from Pierre and Marie Curie University, Paris (1968), he received a Diploma of Advanced Studies (DEA) in Advanced Genetics (1969). Subsequently, instead of preparing the agrégation, that would have ensured a permanent position in the education system, he decided to follow doctorate studies under the supervision of Piotr Slonimski, a Polish-French geneticist, at the CNRS campus of Gif-sur-Yvette, in the southern parisian suburban area. At the same time, he was recruited as a junior scientist by the CNRS (1970), allowing him to complete his PhD thesis, while earning a salary to support his family. He eventually obtained a Doctorate in Natural Sciences, specializing in Genetics, in 1976, from the Pierre and Marie Curie University.
He was a trainee, then attaché, chargé and research master at the CNRS from 1970 to 1983, then a Professor at the Pierre and Marie Curie University from 1983 to 2015, at the same time part-time assistant professor at the Ecole Polytechnique (1984-1988). From 1989 to 1992 he was Head of Laboratory at the Institut Pasteur, then Professor from 1993 to 2015. He was the head of the Unité de Génétique Moléculaire des Levures from 1989 to his retirement in 2015.
Among the other functions occupied during his career, he has been appointed scientific deputy director general of the Institut Pasteur from 2006 to 2008, by the director general, Alice Dautry, and from 1997 to 2011 he was a senior member of the Institut Universitaire de France. He is Emeritus Professor at the Institut Pasteur.
Bernard Dujon scientific work focuses on the genetic material of eukaryotic organisms, its organization, dynamics, functioning and evolution. Most of his work has used the yeast Saccharomyces cerevisiae, as experimental material, but he also got interested in studying other yeasts of biotechnological or medical interest, such as Kluyveromyces lactis and Candida glabrata.
In Gif-sur-Yvette, Bernard Dujon started to study a strange genetic phenomenon, linked to mitochondrial genetics, whose study was still in infancy. When crossing two haploid yeast species carrying different mitochondrial mutations, conferring the resistance to erythromycin or to chloramphenicol, allele segregation did not follow mendelian rules and recombinants appeared in mysterious proportions. At that time, no one had any idea of the genetic content of mitochondria, except that it contained DNA. Bernard Dujon was studying a particular mitochondrial locus, called omega, that could be present as two different alleles, omega+ or omega-. Genetic crosses between yeast cells carrying different alleles led to highly distorted inheritance in the progeny, since almost all cells ended up carrying the omega+ allele! In 1974, he proposed a model in which gene conversion of the omega- allele to omega+ was achieved by homologous recombination, replacing one allele by the other, copying in the process the flanking erythromycin and chloramphenicol mutations.
At about the same time, recombinant DNA technologies and restriction enzymes were discovered. In 1977, independent researches by Fred Sanger on one side and by Walter Gilbert and Allan Maxam on the other, led to the invention of two different methods to sequence DNA. Later the same year, introns were discovered. Thermal denaturation studies with François Michel, another student of Piotr Slonimski, suggested that omega could be an intron. Bernard Dujon contacted Walter Gilbert at Harvard University about the possibility to come to his lab for a short post-doctoral period, in order to sequence the omega locus. He moved to Harvard the following year and in 1979 achieved the sequence of what would become the first mobile intron to be described. But the most surprising result was not that omega was indeed an intron, but that it contained an open reading frame, putatively encoding a 235 amino acid protein with no homology to any known protein. At that time, no intron was supposed to be coding. Could it be that the encoded protein played a role in the intron mobility between omega- and omega+ strains ?
Back to Gif-sur-Yvette in 1981, Bernard Dujon set up a small team in an old lab space lent by Piotr Slonimski. François Michel rapidly joined him and later on Alain Jacquier, Hugues Blanc, Pierre Dehoux and Laurence Colleaux, as well as sabbatical visitors such as Walt Fangman from the University of Washington. They discovered that the omega intron was present in other yeast species collected in Harvard. Following the sequencing of several other introns, François Michel discovered that these introns could be folded into stem-loops whose structures (if not their sequences) were conserved. This suggested that they could be directly involved in the splicing mechanism by defining exon-intron junctions. In addition, they discovered that two different intronic structures existed, defining what they called group I and group II introns, a nomenclature still in use today. They published their models of intron folding in Biochimie in 1982 and this article quickly became a reference for researchers in the field.
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Bernard Dujon
Bernard Dujon is a French geneticist, born on August 8, 1947, in Meudon (Hauts-de-Seine). He is Professor Emeritus at Sorbonne University and the Institut Pasteur since 2015. He is a member of the French Academy of sciences.
Bernard Dujon grew up as a teenager in the Paris suburban area and went to school at Maisons-Lafitte, where his parents settled in 1958. He became interested in biology very early and at the age of eleven started collecting biological material from his natural environment, plants, fossils, insects, shells, etc. He became in 1965 a laureate of the Concours Général, a nation-wide yearly contest, at the same time he was obtaining his baccalauréat. He started a degree of biology at the Faculté des Sciences de Paris the same year. He graduated in the top 1% of students and was offered the opportunity to compete for an oral exam at the prestigious Ecole Normale Supérieure (ENS rue d'Ulm), was ranked first and admitted there the following year (1966). He therefore became a normalien at the early age of 19, when most of the students attracted by this career are still preparing in specialized schools for this written and oral competition. There, he attended lectures at the Faculté de Sciences for two years, before choosing Genetics as a specialization during his third year. After a master's degree in Genetics from Pierre and Marie Curie University, Paris (1968), he received a Diploma of Advanced Studies (DEA) in Advanced Genetics (1969). Subsequently, instead of preparing the agrégation, that would have ensured a permanent position in the education system, he decided to follow doctorate studies under the supervision of Piotr Slonimski, a Polish-French geneticist, at the CNRS campus of Gif-sur-Yvette, in the southern parisian suburban area. At the same time, he was recruited as a junior scientist by the CNRS (1970), allowing him to complete his PhD thesis, while earning a salary to support his family. He eventually obtained a Doctorate in Natural Sciences, specializing in Genetics, in 1976, from the Pierre and Marie Curie University.
He was a trainee, then attaché, chargé and research master at the CNRS from 1970 to 1983, then a Professor at the Pierre and Marie Curie University from 1983 to 2015, at the same time part-time assistant professor at the Ecole Polytechnique (1984-1988). From 1989 to 1992 he was Head of Laboratory at the Institut Pasteur, then Professor from 1993 to 2015. He was the head of the Unité de Génétique Moléculaire des Levures from 1989 to his retirement in 2015.
Among the other functions occupied during his career, he has been appointed scientific deputy director general of the Institut Pasteur from 2006 to 2008, by the director general, Alice Dautry, and from 1997 to 2011 he was a senior member of the Institut Universitaire de France. He is Emeritus Professor at the Institut Pasteur.
Bernard Dujon scientific work focuses on the genetic material of eukaryotic organisms, its organization, dynamics, functioning and evolution. Most of his work has used the yeast Saccharomyces cerevisiae, as experimental material, but he also got interested in studying other yeasts of biotechnological or medical interest, such as Kluyveromyces lactis and Candida glabrata.
In Gif-sur-Yvette, Bernard Dujon started to study a strange genetic phenomenon, linked to mitochondrial genetics, whose study was still in infancy. When crossing two haploid yeast species carrying different mitochondrial mutations, conferring the resistance to erythromycin or to chloramphenicol, allele segregation did not follow mendelian rules and recombinants appeared in mysterious proportions. At that time, no one had any idea of the genetic content of mitochondria, except that it contained DNA. Bernard Dujon was studying a particular mitochondrial locus, called omega, that could be present as two different alleles, omega+ or omega-. Genetic crosses between yeast cells carrying different alleles led to highly distorted inheritance in the progeny, since almost all cells ended up carrying the omega+ allele! In 1974, he proposed a model in which gene conversion of the omega- allele to omega+ was achieved by homologous recombination, replacing one allele by the other, copying in the process the flanking erythromycin and chloramphenicol mutations.
At about the same time, recombinant DNA technologies and restriction enzymes were discovered. In 1977, independent researches by Fred Sanger on one side and by Walter Gilbert and Allan Maxam on the other, led to the invention of two different methods to sequence DNA. Later the same year, introns were discovered. Thermal denaturation studies with François Michel, another student of Piotr Slonimski, suggested that omega could be an intron. Bernard Dujon contacted Walter Gilbert at Harvard University about the possibility to come to his lab for a short post-doctoral period, in order to sequence the omega locus. He moved to Harvard the following year and in 1979 achieved the sequence of what would become the first mobile intron to be described. But the most surprising result was not that omega was indeed an intron, but that it contained an open reading frame, putatively encoding a 235 amino acid protein with no homology to any known protein. At that time, no intron was supposed to be coding. Could it be that the encoded protein played a role in the intron mobility between omega- and omega+ strains ?
Back to Gif-sur-Yvette in 1981, Bernard Dujon set up a small team in an old lab space lent by Piotr Slonimski. François Michel rapidly joined him and later on Alain Jacquier, Hugues Blanc, Pierre Dehoux and Laurence Colleaux, as well as sabbatical visitors such as Walt Fangman from the University of Washington. They discovered that the omega intron was present in other yeast species collected in Harvard. Following the sequencing of several other introns, François Michel discovered that these introns could be folded into stem-loops whose structures (if not their sequences) were conserved. This suggested that they could be directly involved in the splicing mechanism by defining exon-intron junctions. In addition, they discovered that two different intronic structures existed, defining what they called group I and group II introns, a nomenclature still in use today. They published their models of intron folding in Biochimie in 1982 and this article quickly became a reference for researchers in the field.
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