Trans regulation in the Ultrabithorax gene of Drosophila: alterations in the promoter enhance transvection

PMCID: PMC556824We report a genetic and molecular study of UbxMX6 and Ubx195rx1, two mutations in the Ultrabithorax (Ubx) locus which appear to have a strong effect on the activity of the homologous Ubx gene. These mutations show the characteristic embryonic and adult phenotypes of Ubx null alleles, and also fail to produce any detectable Ubx product. Yet, genetic and phenotypic analyses involving a large number of trans heterozygous combinations of UbxMX6 and Ubx195rx1 with different classes of Ubx mutations, indicate that they hyperactivate the homologous gene. This effect is induced on wildtype or mutant forms of Ubx, provided that the pairing in the bithorax region is normal, i.e. these mutations have a strong positive effect on transvection. We also show that, unlike all the other known cases of transvection in Ubx, this is not zeste-dependent. Southern analyses indicate that UbxMX6 is a 3.4 kb deletion, and Ubx195rx1 is an approximately 11 kb insertion of foreign DNA, both in the promoter region. We speculate that the region altered in the mutations may have a wildtype function to ensure cis-autonomy of the regulation of Ubx transcription.This work was supported by grants from the DGICYT and the Fundación Ramón Areces.Peer reviewe

Mutations of RNA polymerase II activate key genes of the nucleoside triphosphate biosynthetic pathways

The yeast URA2 gene, encoding the rate-limiting enzyme of UTP biosynthesis, is transcriptionally activated by UTP shortage. In contrast to other genes of the UTP pathway, this activation is not governed by the Ppr1 activator. Moreover, it is not due to an increased recruitment of RNA polymerase II at the URA2 promoter, but to its much more effective progression beyond the URA2 mRNA start site(s). Regulatory mutants constitutively expressing URA2 resulted from cis-acting deletions upstream of the transcription initiator region, or from amino-acid replacements altering the RNA polymerase II Switch 1 loop domain, such as rpb1-L1397S. These two mutation classes allowed RNA polymerase to progress downstream of the URA2 mRNA start site(s). rpb1-L1397S had similar effects on IMD2 (IMP dehydrogenase) and URA8 (CTP synthase), and thus specifically activated the rate-limiting steps of UTP, GTP and CTP biosynthesis. These data suggest that the Switch 1 loop of RNA polymerase II, located at the downstream end of the transcription bubble, may operate as a specific sensor of the nucleoside triphosphates available for transcription

A Viable Hypomorphic Allele of the Essential IMP3 Gene Reveals Novel Protein Functions in Saccharomyces cerevisiae

In Saccharomyces cerevisiae, the essential IMP3 gene encodes a component of the SSU processome, a large ribonucleoprotein complex required for processing of small ribosomal subunit RNA precursors. Mutation of the IMP3 termination codon to a sense codon resulted in a viable mutant allele producing a C-terminal elongated form of the Imp3 protein. A strain expressing the mutant allele displayed ribosome biogenesis defects equivalent to IMP3 depletion. This hypomorphic allele represented a unique opportunity to investigate and better understand the Imp3p functions. We demonstrated that the +1 frameshifting was increased in the mutant strain. Further characterizations revealed involvement of the Imp3 protein in DNA repair and telomere length control, pointing to a functional relationship between both pathways and ribosome biogenesis

Evaluation of Visual and Patient—Reported Outcomes, Spectacle Dependence after Bilateral Implantation with a Non-Diffractive Extended Depth of Focus Intraocular Lens Compared to Other Intraocular Lenses

Purpose: To evaluate postoperative outcomes, spectacle dependance and the occurrence of the photic phenomena in patients after cataract surgery following the implantation of a non-diffractive extended depth of focus (EDOF) intraocular lens was compared to monofocal and multifocal lenses. Methods: We enrolled patients with bilateral cataracts who wanted to reduce their dependence on glasses in the study. They were followed for 6 months. The study group in which the EDOF lens was implanted consisted of 70 eyes in 35 patients. The control groups consisted of: 52 eyes in 26 patients in whom a multifocal was implanted and 52 eyes in 26 patients with implanted monofocal lens. After a total of 2 weeks, 2 months and 6 months post-surgery the following were evaluated: uncorrected and corrected visual acuity at 4 m, 80 cm, 40 cm, manifest refraction expressed as mean refractive spherical equivalent (MRSE), contrast sensitivity, intraocular pressure. A questionnaire on independence from ocular correction, the occurrence of photic phenomena, and patient satisfaction was also completed. Results: Monocular and binocular visual acuity and MRSE 6 months after the procedure were compared between three groups. All of the main analyses, except for comparisons of uncorrected distance visual acuity (both monocular and binocular) level, were significant. Contrast sensitivity was lower among patients with multifocal lens than among patients with EDOF lens. Halo and glare after 6 months were seen more often among patients with multifocal lens than among patients with the other lens (65% of eyes with multifocal lens vs. 6% of eyes with EDOF lens and 0% of eyes with monofocal lens). Glasses were needed by 35% of patients with EDOF lens, and by 96% of patients with monofocal lens and in none of the patients with multifocal lens. Conclusions: Most patients qualify for the implantation of a non-diffractive EDOF lens. Post-operative visual acuity improves at any distance. The best monocular visual acuity for intermediate distances is provided by an EDOF lens, and for near distance by a multifocal lens. The EDOF lens definitely increases independence from spectacle correction compared to monofocal lenses; however, the greatest degree of independence from spectacles is provided by multifocal lenses. The incidence of photic phenomena is slightly higher than that of a monofocal lens, and much lower for a multifocal lens

Cataract Surgery after Radial Keratotomy with Non-Diffractive Extended Depth of Focus Lens Implantation

Radial keratotomy was a popular surgical procedure used to treat myopia. Patients who underwent radial keratotomy several years ago, are currently reporting to the ophthalmologist due to worsening of vision associated with age-related cataracts. In this case report we present a case of a 60-year-old woman who underwent radial keratotomy with 16 incisions in the right eye and 12 incisions in the left eye. The patient reported to an ophthalmologist due to a deterioration of vision caused by a cataract. We described, in detail, the difficulties encountered during the diagnostic procedures, differences in the calculation of intraocular lens, and intraoperative difficulties as compared to patients who had not undergone radial keratotomy. We also present the obtained postoperative results

Synthesis and Anti-Yeast Evaluation of Novel 2-Alkylthio-4-chloro-5-methyl-N-[imino-(1-oxo-(1H)-phthalazin-2-yl)methyl]benzenesulfonamide Derivatives

Pathogenic fungi are one of the main causes of hospital-related infections. Since conventional antifungals have become less effective because of the increasing fungal resistance to the standard drugs, the need for new agents is becoming urgent. Herein we report a synthesis of a series of novel N-[imino-(1-oxo-(1H)-phthalazin-2-yl)methyl]-benzenesulfonamide derivatives with in vitro activity against yeast-like fungi isolated from the oral cavity and respiratory tract of patients with candidiasis. These compounds were synthesized by the one-step or two-step reactions of 1-(2-alkylthiobenzensulfonyl)-2-aminoguanidines with the appropriate ortho-carbonyl benzoic acids. The biological study revealed that new derivatives have shown significant growth-inhibitory activity, superior or comparable, than those of the reference drug fluconazole. The most promising activities were observed against Candida albicans, with inhibition at least 1–3 (12.5%–37.5%) of the eight tested strains at the low MIC level of ≤6.2–25 µg/mL

Rsp5 ubiquitin ligase affects isoprenoid pathway and cell wall organization in S. cerevisiae.

Dimethylallyl diphosphate, an isomer of isopentenyl diphosphate, is a common substrate of Mod5p, a tRNA modifying enzyme, and the farnesyl diphosphate synthase Erg20p, the key enzyme of the isoprenoid pathway. rsp5 mutants, defective in the Rsp5 ubiquitin-protein ligase, were isolated and characterized as altering the mitochondrial/cytosolic distribution of Mod5p. To understand better how competition for the substrate determines the regulation at the molecular level, we analyzed the effect of the rsp5-13 mutation on Erg20p expression. The level of Erg20p was three times lower in rsp5-13 compared to the wild type strain and this effect was dependent on active Mod5p. Northern blot analysis indicated a regulatory role of Rsp5p in ERG20 transcription. ERG20 expression was also impaired in pkc1Δ lacking a component of the cell wall integrity signaling pathway. Low expression of Erg20p in rsp5 cells was accompanied by low level of ergosterol, the main end product of the isoprenoid pathway. Additionally, rsp5 strains were resistant to nystatin, which binds to ergosterol present in the plasma membrane, and sensitive to calcofluor white, a drug destabilizing cell wall integrity by binding to chitin. Furthermore, the cell wall structure appeared abnormal in most rsp5-13 cells investigated by electron microscopy and chitin level in the cell wall was increased two-fold. These results indicate that Rsp5p affects the isoprenoid pathway which has important roles in ergosterol biosynthesis, protein glycosylation and transport and in this way may influence the composition of the plasma membrane and cell wall

Expression of Subtelomeric lncRNAs Links Telomeres Dynamics to RNA Decay in S. cerevisiae

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