Biomedical subjects

E Ramil

Publications and source records attributed to E Ramil.

8 recordsLinked to original sources

PubMed2001

The KlCYC1 gene, a downstream region for two differentially regulated transcripts.

KlCYC1 encodes for cytochrome c in the yeast Kluyveromyces lactis and is transcribed in two mRNAs with different 3'-processing points. This is an uncommon transcription mechanism in yeast mRNAs. The 3' sequence encompassing the whole region that is needed to produce both mRNAs is analysed. We have determined identical processing points in K.lactis and in Saccharomyces cerevisiae cells transformed with KlCYC1; positions 698 and 1092 (with respect to the TAA) are the major polyadenylation points. This shows that the cis-elements present in the KlCYC1 3'-untranslated region (3'-UTR) direct a processing mechanism that has been conserved in yeast. In K. lactis there is a high predominance of the shorter transcript (1.14 kb) only at the initial logarithmic growth phase. Interestingly, this growth phase-dependent regulation of 3'-UTR processing is lost when the gene is expressed in S. cerevisiae.

3' Untranslated Regions↗

PubMed2000

Respirofermentative metabolism in Kluyveromyces lactis: Insights and perspectives.

Yeasts do not form a homogeneous group as far as energy-yielding metabolism is concerned and the fate of pyruvate, a glycolytic intermediate, determines the type of energy metabolism. Kluyveromyces lactis has become an alternative to the traditional yeast Saccharomyces cerevisiae owing to its industrial applications as well as to studies on mitochondrial respiration. In this review we summarize the current knowdeledge about the K. lactis respirofermentative metabolism, taking into account the respiratory capacity of this yeast and the molecular mechanisms controlling its regulation, giving an up-to-date picture.

Journal Article↗

PubMed2000

Heme-mediated transcriptional control in Kluyveromyces lactis.

Heme is of great importance in oxygen-dependent biological functions, since it serves as a prosthetic group for many proteins related to oxygen-binding, oxidative damage prevention and electron transport. It also regulates gene expression through the action of specific transcriptional regulatory factors. In this paper, we present an analysis of heme-dependent transcriptional regulation of several respiration-related genes in an aerobic respiratory yeast, Kluyveromyces lactis. We also report that the KlHEM13 gene, encoding the heme biosynthetic enzyme coproporphyrinogen oxidase, is under heme and oxygen transcriptional regulation, thereby controlling the synthesis of the effector, heme. KlHEM13 is induced during hypoxia, which represents the first report of a transcriptionally regulated gene with this behaviour in K. lactis.

Base Sequence↗

PubMed2000

Regulation of the CYB2 gene expression: transcriptional co-ordination by the Hap1p, Hap2/3/4/5p and Adr1p transcription factors.

Expression of the Saccharomyces cerevisiae nuclear gene CYB2 encoding the mitochondrial enzyme L-(+)-lactate-cytochrome c oxidoreductase (EC 1.2.2.3) is subject to several strict metabolic controls at the transcriptional level: repression due to glucose fermentation, derepression by ethanol, induction by lactate and inhibition under anaerobic conditions or in response to deficiency of haem biosynthesis. In this respect, the data obtained from the transcriptional analysis of the CYB2 gene contribute to a better understanding of the control of mitochondrial biogenesis. In this study, we show that Hap1p is the main transcriptional activator involved in the control of CYB2 transcription. We found that Hap1p activity, known to be oxygen dependent, is effected by DNA-protein interaction with two binding sites present in the CYB2 promoter. Control is moreover dependent on carbon sources. This regulation by the carbon substrates is subordinate to the activity of the complex Hap2/3/4/5p, which counteracts the negative effect of the URS1 element. Finally, our results suggest that the Adr1p transcriptional activator is also required in CYB2 transcription control. This work provides new data which allows a better understanding of the molecular mechanisms implicated in the co-regulation at the transcriptional level of the genes encoding proteins involved in various aspects of oxidative metabolism.

Animals↗

PubMed1998

Characterization of promoter regions involved in high expression of KlCYC1.

Functional analysis of the KlCYC1 promoter reveals that sequences located upstream to those already published [Freire-Picos, M. A., Rodríguez-Torres, A. M., Ramil, E., Cerdán, M. E., Breuning, K. D., Hollenberg, C. P. & Zitomer, R. S. (1993) Sequence of a cytochrome c from Kluyveromyces lactis and its upstream region, Yeast 9, 201-204] and extending from positions -780 to -371 are important for maintaining high levels of expression, although this region contains both negative and positive elements. A consensus sequence for interaction with KlCpf1p is present at position -492, into the negative site, and specific protein binding to KlCpf1p has been demonstrated. Deletion of the sequences from positions -413 to -338 diminishes KlCYC1 transcription; protein binding to two sequences included in this activator region is detected and several points of evidence indicate that the complex observed is different from the Hap2/3/4/5p complex. Binding of KlCpf1p and the activator complex to the promoter is constitutive in different carbon sources. Although the promoter contains CCAAT boxes, directed mutagenesis has revealed that they are not related to the moderate de-repression observed in glycerol media.

Base Sequence↗

PubMed1996

Sequence analysis of a 10 kb DNA fragment from yeast chromosome VII reveals a novel member of the DnaJ family.

We report the sequence analysis of a 10 kb DNA fragment of Saccharomyces cerevisiae chromosome VII. This sequence contains four complete open reading frames (ORFs) of greater than 100 amino acids. There are also two incomplete ORFs flanking the extremes: one of these, G2868, is the 5' part of the SCS3 gene (Hosaka et al., 1994). ORFs G2853 and G2856 correspond to the genes CEG1, coding for the alfa subunit of the mRNA guanylyl transferase and a 3' gene of unknown function previously sequenced (Shibagaki et al., 1992). G2864 is identical to SOH1 also reported (Fan and Klein, 1994).

Amino Acid Sequence↗

PubMed1994

Codon usage in Kluyveromyces lactis and in yeast cytochrome c-encoding genes.

Codon usage (CU) in Kluyveromyces lactis has been studied. Comparison of CU in highly and lowly expressed genes reveals the existence of 21 optimal codons; 18 of them are also optimal in other yeasts like Saccharomyces cerevisiae or Candida albicans. Codon bias index (CBI) values have been recalculated with reference to the assignment of optimal codons in K. lactis and compared to those previously reported in the literature taking as reference the optimal codons from S. cerevisiae. A new index, the intrinsic codon deviation index (ICDI), is proposed to estimate codon bias of genes from species in which optimal codons are not known; its correlation with other index values, like CBI or effective number of codons (Nc), is high. A comparative analysis of CU in six cytochrome-c-encoding genes (CYC) from five yeasts is also presented and the differences found in the codon bias of these genes are discussed in relation to the metabolic type to which the corresponding yeasts belong. Codon bias in the CYC from K. lactis and S. cerevisiae is correlated to mRNA levels.

Amino Acids↗

PubMed1993

Sequence of a cytochrome c gene from Kluyveromyces lactis and its upstream region.

The complete sequence of a cytochrome c gene from Kluyveromyces lactis including its upstream region is reported. Sequence of the translated open reading frame is discussed in terms of cytochrome c structural requirements. Putative regulatory signals in the upstream region are described and compared with reported sequences which modulate the expression of respiratory-related yeast genes.

Amino Acid Sequence↗