Diauxic Inhibition: Jacques Monod's Ignored Work.

Diauxie is at the origin of research that led Jacques Monod (1910-1976), François Jacob (1920-2013), and André Lwoff (1902-1994) to win the Nobel Prize in Physiology or Medicine in 1965 for their description of the first genetic regulatory model. Diauxie is a term coined by Jacques Monod in 1941 in his doctoral dissertation that refers to microbial growth in two phases. In this article, we first examine Monod's thesis to demonstrate how and why Monod interpreted diauxie as a phenomenon of enzyme inhibition or suppression of adaptive enzymes.

Checkpoint-dependent and -independent roles of Swi3 in replication fork recovery and sister chromatid cohesion in fission yeast.

Multiple genome maintenance processes are coordinated at the replication fork to preserve genomic integrity. How eukaryotic cells accomplish such a coordination is unknown. Swi1 and Swi3 form the replication fork protection complex and are involved in various processes including stabilization of replication forks, activation of the Cds1 checkpoint kinase and establishment of sister chromatid cohesion in fission yeast.

Novel relationships among DNA methylation, histone modifications and gene expression in Ascobolus.

By studying Ascobolus strains methylated in various portions of the native met2 gene or of the hph transgene, we generalized our previous observation that methylation of the downstream portion of a gene promotes its stable silencing and triggers the production of truncated transcripts which rarely extend through the methylated region. In contrast, methylation of the promoter region does not promote efficient gene silencing. The chromatin state of met2 methylated strains was investigated after partial micrococcal nuclease (MNase) digestion.

Molecular and cellular dissection of mating-type switching steps in Schizosaccharomyces pombe.

A strand-specific imprint (break) controls mating-type switching in fission yeast. By introducing a thiamine repressible promoter upstream of the mat1 locus, we can force transcription through the imprinted region, erasing the imprint and inhibiting further mating-type switching, in a reversible manner. Starting from a synchronized, virgin M-cell population, we show that the site- and strand-specific break is formed when DNA replication intermediates appear at mat1 during the first S phase.

Role of DNA replication proteins in double-strand break-induced recombination in Saccharomyces cerevisiae.

Mitotic double-strand break (DSB)-induced gene conversion involves new DNA synthesis. We have analyzed the requirement of several essential replication components, the Mcm proteins, Cdc45p, and DNA ligase I, in the DNA synthesis of Saccharomyces cerevisiae MAT switching. In an mcm7-td (temperature-inducible degron) mutant, MAT switching occurred normally when Mcm7p was degraded below the level of detection, suggesting the lack of the Mcm2-7 proteins during gene conversion.

Formation, maintenance and consequences of the imprint at the mating-type locus in fission yeast.

Mating-type switching in the fission yeast Schizosaccharomyces pombe is initiated by a strand-specific imprint located at the mating-type (mat1) locus. We show that the imprint corresponds to a single-strand DNA break (SSB), which is site- but not sequence-specific. We identified three novel cis-acting elements, involved in the formation and stability of the SSB.