Ty1 extrachromosomal circular copies in Saccharomyces cerevisiae

AbstractThe eukaryotic transposable element Ty1 is present in about 20–30 integrated copies per yeast aploid genome, variably localized in different strains. Here, we report the presence in yeast of circular extrachromosomal molecules homologous to Ty1, 6 kilobases in size (the same as integrated copies) present in about 1 circular copy/250–300 cells. This finding shows another analogy between eurkaryotic-transposable elements and the pro-viral integrative form of retroviruses

Epigenetic and posttranslational modifications in light signal transduction and the circadian clock in Neurospora crassa

Blue light, a key abiotic signal, regulates a wide variety of physiological processes in many organisms. One of these phenomena is the circadian rhythm presents in organisms sensitive to the phase-setting effects of blue light and under control of the daily alternation of light and dark. Circadian clocks consist of autoregulatory alternating negative and positive feedback loops intimately connected with the cellular metabolism and biochemical processes. Neurospora crassa provides an excellent model for studying the molecular mechanisms involved in these phenomena. The White Collar Complex (WCC), a blue-light receptor and transcription factor of the circadian oscillator, and Frequency (FRQ), the circadian clock pacemaker, are at the core of the Neurospora circadian system. The eukaryotic circadian clock relies on transcriptional/translational feedback loops: some proteins rhythmically repress their own synthesis by inhibiting the activity of their transcriptional factors, generating self-sustained oscillations over a period of about 24 h. One of the basic mechanisms that perpetuate self-sustained oscillations is post translation modification (PTM). The acronym PTM generically indicates the addition of acetyl, methyl, sumoyl, or phosphoric groups to various types of proteins. The protein can be regulatory or enzymatic or a component of the chromatin. PTMs influence protein stability, interaction, localization, activity, and chromatin packaging. Chromatin modification and PTMs have been implicated in regulating circadian clock function in Neurospora. Research into the epigenetic control of transcription factors such as WCC has yielded new insights into the temporal modulation of light-dependent gene transcription. Here we report on epigenetic and protein PTMs in the regulation of the Neurospora crassa circadian clock. We also present a model that illustrates the molecular mechanisms at the basis of the blue light control of the circadian clock

“White Collar 1, a central regulator of blue light response in Neurospora, is a Zinc finger protein”

The Neurospora crassa blind mutant white collar-1 (wc-1) is pleiotropically defective in all blue light-induced phenomena, establishing a role for the wc-1 gene product in the signal transduction pathway. We report the cloning of the wc-1 gene isolated by chromosome walking and mutant complementation. The elucidation of the wc-1 gene product provides a key piece of the blue light signal transduction puzzle. The wc-1 gene encodes a 125 kDa protein whose encoded motifs include a single class four, zinc finger DNA binding domain and a glutamine-rich putative transcription activation domain. We demonstrate that the wc-1 zinc finger domain, expressed in Escherichia coli, is able to bind specifically to the promoter of a blue light-regulated gene of Neurospora using an in vitro gel retardation assay. Furthermore, we show that wc-1 gene expression is autoregulated and is transcriptionally induced by blue light irradiation.The Neurospora crassa blind mutant white collar-1 (wc-1) is pleiotropically defective in all blue light-induced phenomena, establishing a role for the wc-1 gene product in the signal transduction pathway. We report the cloning of the wc-1 gene isolated by chromosome walking and mutant complementation. The elucidation of the wc-1 gene product provides a key piece of the blue light signal transduction puzzle. The wc-1 gene encodes a 125 kDa protein whose encoded motifs include a single class four, zinc finger DNA binding domain and a glutamine-rich putative transcription activation domain. We demonstrate that the wc-1 zinc finger domain, expressed in Escherichia coli, is able to bind specifically to the promoter of a blue light-regulated gene of Neurospora using an in vitro gel retardation assay. Furthermore, we show that wc-1 gene expression is autoregulated and is transcriptionally induced by blue light irradiation

The Neurospora crassa carotenoid biosynthetic gene (albino 3) reveals highly conserved regions among prenyltransferases.

In the filamentous fungus Neurospora crassa the biosynthesis of carotenoids is regulated by blue light. Here we report the characterization of the albino-3 (al-3) gene of N. crassa, which encodes the carotenoid biosynthetic enzyme geranylgeranyl-pyrophosphate synthetase. This is the first geranylgeranyl-pyrophosphate synthetase gene isolated. Nucleotide sequence comparison of al-3 genomic and cDNA clones revealed that the al-3 gene is not interrupted by introns. Transcription of the al-3 gene has been examined in dark-grown and light-induced mycelia. The analysis revealed that the al-3 gene is not expressed in the dark and that its transcription is induced by blue light (Nelson, M. A., Morelli, G., Carattoli, A., Romano, N., and Macino, G. (1989) Mol. Cell. Biol. 9, 1271-1276). The al-3 gene encodes a polypeptide of 428 amino acids. Comparison of the deduced amino acid sequence of al-3 with the sequences of prenyltransferases of other species, from bacteria to humans, showed three highly conserved homologous regions. These homologous regions may be involved in the formation of the catalytic site of the prenyltransferases

Retroperitoneal and Retrograde Total Laparoscopic Hysterectomy – Technique with Three- and Five-millimeter Trocars

In this chapter, we describe total laparoscopic hysterectomy (TLH) using retroperitoneal and retrograde technique: it combines the retroperitoneal coagulation of the uterine artery and the retrograde approach to the pelvic organs, as in oncological surgeries. We report our experience in applying this modified TLH with 3-mm instruments and without uterine manipulator, in order to demonstrate its safety and feasibility

Périgord black truffle genome uncovers evolutionary origins and mechanisms of symbiosis

LetterInternational audienceThe Périgord black truffle ($Tuber\ melanosporum$ Vittad.) and the Piedmont white truffle dominate today's truffle market. The hypogeous fruiting body of $T.\ melanosporum$ is a gastronomic delicacy produced by an ectomycorrhizal symbiont endemic to calcareous soils in southern Europe. The worldwide demand for this truffle has fuelled intense efforts at cultivation. Identification of processes that condition and trigger fruit body and symbiosis formation, ultimately leading to efficient crop production, will be facilitated by a thorough analysis of truffle genomic traits. In the ectomycorrhizal $Laccaria\ bicolor$, the expansion of gene families may have acted as a 'symbiosis toolbox'. This feature may however reflect evolution of this particular taxon and not a general trait shared by all ectomycorrhizal species. To get a better understanding of the biology and evolution of the ectomycorrhizal symbiosis, we report here the sequence of the haploid genome of $T.\ melanosporum$, which at $\sim$125 megabases is the largest and most complex fungal genome sequenced so far. This expansion results from a proliferation of transposable elements accounting for $\sim$58% of the genome. In contrast, this genome only contains $\sim$7,500 protein-coding genes with very rare multigene families. It lacks large sets of carbohydrate cleaving enzymes, but a few of them involved in degradation of plant cell walls are induced in symbiotic tissues. The latter feature and the upregulation of genes encoding for lipases and multicopper oxidases suggest that $T.\ melanosporum$ degrades its host cell walls during colonization. Symbiosis induces an increased expression of carbohydrate and amino acid transporters in both $L.\ bicolor$ and $T.\ melanosporum$, but the comparison of genomic traits in the two ectomycorrhizal fungi showed that genetic predispositions for symbiosis $-$'the symbiosis toolbox'$-$ evolved along different ways in ascomycetes and basidiomycete