Expression of three genes for elongation factor 1 alpha during morphogenesis of Mucor racemosus

Multiple isoforms for the catalytic subunit of PKA in the basal fungal lineage Mucor circinelloides

Protein kinase A (PKA) activity is involved in dimorphism of the basal fungal lineage Mucor. From the recently sequenced genome of Mucor circinelloides we could predict ten catalytic subunits of PKA. From sequence alignment and structural prediction we conclude that the catalytic core of the isoforms is conserved, and the difference between them resides in their amino termini. This high number of isoforms is maintained in the subdivision Mucoromycotina. Each paralogue, when compared to the ones form other fungi is more homologous to one of its orthologs than to its paralogs. All of these fungal isoforms cannot be included in the class I or II in which fungal protein kinases have been classified. mRNA levels for each isoform were measured during aerobic and anaerobic growth. The expression of each isoform is differential and associated to a particular growth stage. We reanalyzed the sequence of PKAC (GI 20218944), the only cloned sequence available until now for a catalytic subunit of M. circinelloides. PKAC cannot be classified as a PKA because of its difference in the conserved C-tail; it shares with PKB a conserved C2 domain in the N-terminus. No catalytic activity could be measured for this protein nor predicted bioinformatically. It can thus be classified as a pseudokinase. Its importance can not be underestimated since it is expressed at the mRNA level in different stages of growth, and its deletion is lethal.

Elongation factor 1β' gene from Spodoptera exigua: characterization and function identification through RNA interference

Elongation factor (EF) is a key regulation factor for translation in many organisms, including plants, bacteria, fungi, animals and insects. To investigate the nature and function of elongation factor 1β′ from Spodoptera exigua (SeEF-1β′), its cDNA was cloned. This contained an open reading frame of 672 nucleotides encoding a protein of 223 amino acids with a predicted molecular weight of 24.04 kDa and pI of 4.53. Northern blotting revealed that SeEF-1β′ mRNA is expressed in brain, epidermis, fat body, midgut, Malpighian tubules, ovary and tracheae. RT-PCR revealed that SeEF-1β′ mRNA is expressed at different levels in fat body and whole body during different developmental stages. In RNAi experiments, the survival rate of insects injected with SeEF-1β′ dsRNA was 58.7% at 36 h after injection, which was significantly lower than three control groups. Other elongation factors and transcription factors were also influenced when EF-1β′ was suppressed. The results demonstrate that SeEF-1β′ is a key gene in transcription in S. exigua.

Molecular systematics in the genus Mucor with special regards to species encountered in cheese

The genus Mucor, a member of the order Mucorales, comprises different species encountered in cheeses. Although fungi play a fundamental role in cheese manufacturing and ripening, the taxonomy of many fungal species found in cheese is poorly defined; indeed, this is the case for Mucor spp. In the present study, we assessed the phylogenetic relationships among 70 Mucor strains, including 36 cheese isolates, by using a five gene phylogenetic approach combined with morphological analyses. Overall, at least six species of Mucor were identified among the cheese isolates including a possible new taxon. The present study also suggests that the genus Mucor comprises undescribed taxa and needs to be properly defined.

Distribution of elongation factor-1alpha in larval tissues of the fall armyworm, Spodoptera frugiperda

Elongation factor-1alpha (EF-1alpha) promotes the delivery of aminoacyl-tRNA to the acceptor site of the ribosome during protein synthesis. The enzyme has a number of additional functions, including regulation of apoptosis and interaction with the cytoskeleton. We determined the distribution of EF-1alpha in larval tissues of the fall armyworm, Spodoptera frugiperda , with a monoclonal antibody generated to EF-1alpha from Sf21 cells, a cell line developed from ovarian tissue of S. frugiperda. Enzyme-linked immunosorbent assay showed that EF-1alpha comprised 1.9-9.9% of the total protein within the tissues that were examined, which included fat body, Malpighian tubules, midgut, muscle, salivary glands, trachea, and ventral nerve cord. To a certain extent, EF-1alpha concentrations reflected the expected metabolic activity level of each of the represented tissues. Closer examination by immunofluorescence microscopy revealed that EF-1alpha concentrations varied among different cell types within a given tissue, i.e. midgut columnar epithelial cells yielded strong signals, while goblet cells failed to react with the EF-1alpha-specific antibody.

Monoclonal antibodies to elongation factor-1alpha inhibit in vitro translation in lysates of Sf21 cells

Elongation factor-1alpha (EF-1alpha) is an enzyme that is essential for protein synthesis. Although EF-1alpha offers an excellent target for the disruption of insect metabolism, agents known to interfere with EF-1alpha activity are toxic to humans. In this article, we describe the development of monoclonal antibodies (MAbs) that can disrupt the activity of insect EF-1alpha without cross-reacting with the human enzyme. MAbs were generated to EF-1alpha from Sf21 cells derived from the fall armyworm, Spodoptera frugiperda, by immunizing mice with EF-1alpha eluted from SDS-PAGE gels. The MAbs reacted with EF-1alpha in eggs and first through fifth instars of the fall armyworm in immunoblots of SDS-PAGE gels, but did not recognize EF-1alpha in human carcinoma cells and normal tissues. MAbs with the ability to recognize EF-1alpha in its native conformation, identified through immunoprecipitation experiments, were added to Sf21 cell lysates to determine whether the antibodies could inhibit incorporation of [(35)S]methionine into newly synthesized in vitro translation products. Of the four EF-1alpha-specific MAbs tested, three significantly inhibited protein synthesis when compared to the negative control antibody (P < 0.001, one-way ANOVA; followed by Dunnett's test, P < 0.05).

Evidence that MRas1 and MRas3 proteins are associated with distinct cellular functions during growth and morphogenesis in the fungus Mucor racemosus

The filamentous fungus Mucor racemosus provides a simple and unique model system for defining the function of individual ras genes in a gene family which is closely related to mammalian ras genes. The current study was designed to investigate the role of Mras1 and Mras3 in different stages of fungal morphogenesis, including sporangiospore germination, sporulation, and dimorphic transitions. The overall patterns of Mras1 and Mras3 transcript and protein accumulation were markedly different but, in general, transcripts and proteins were present at low levels during spherical growth and their accumulated level increased severalfold during polar growth (germ tube emergence and elongation). In contrast to Mras1, relatively high levels of Mras3 transcript accumulated during sporulation and MRas3 protein accumulated in sporangiospores. Transformation of M. racemosus with an activated allele of Mras3 reduced growth rate during aerobic sporangiospore germination, while a dominant-negative allele of Mras3 caused a 40% decrease in viable asexual spores. An activated allele of Mras1 increased growth rate during sporangiospore germination but neither activated nor dominant-negative alleles of Mras1 affected total number of asexual spores. Expression of MRas3 and MRas1 proteins appear to be subject to different regulatory mechanisms: exogenous dibutyryl-cAMP and fusidienol caused a strong repression of the level of MRas3 protein (but not MRas1) concurrent with the inhibition of polar growth. Differential posttranslational modification and intracellular localization of MRas1 and MRas3 proteins were also observed. The data strongly suggest that Mras3 and Mras1 play different roles in regulation of cell growth and morphogenesis in Mucor.

Cloning of aSchizosaccharomyces pombehomologue of elongation factor 1 alpha by two-hybrid selection of calmodulin-binding proteins

This study reports the cloning and characterization of a cDNA encoding elongation factor 1-alpha (EF1alpha) from the yeast Schizosaccharomyces pombe. The cDNA was cloned from an Schizosaccharomyces pombe expression library by a two-hybrid selection for clones encoding calmodulin (CaM)-binding proteins. The predicted protein is highly homologous to mammalian EF1alpha, indicating a strong tendency towards conservation of the primary amino acid sequence. The protein was expressed as a glutathione S-transferase fusion in both bacteria and in Schizosaccharomyces pombe. The bacterial protein was shown by solution assay to compete with CaM kinase II for CaM. The CaM binding domain was localized to the C-terminus of the protein by this method. Expression of full-length EF1alpha in vivo caused an increase in cell cycle length and a decreased rate of growth as evidenced by a lack of elongated cells in slowly dividing cultures. This effect appears to involve CaM binding because a truncation mutant version of EF1alpha lacking the CaM binding domain did not cause cell cycle delay.Key words: calmodulin, two-hybrid selection, calmodulin-binding protein, yeast, cell proliferation.

Malaria parasites contain two identical copies of an elongation factor 1 alpha gene

Elongation factor 1alpha (EF-1alpha) is an abundant protein in eukaryotic cells, involved chiefly in translation of mRNA on the ribosomes, and is frequently encoded by more than one gene. Here we show the presence of two identical copies of the EF-1alpha gene in the genome of three malaria parasites, Plasmodium knowlesi, P. berghei and P. falciparum. They are organized in a head-to-head orientation and both genes are expressed in a stage specific manner at a high level, indicating that the small intergenic region contains either two strong promoters or a single bidirectional one. Both genes are expressed at the same time during erythrocytic development of the parasite. This expression pattern and the 100% similarity of the two genes excludes the possibility that the duplicated genes developed in accordance to the different types of ribosomes in Plasmodium. It is more likely that the duplication reflects a gene dosage effect. Comparison of codon usage in the Cdc2-related kinase genes (CRK2) of Plasmodium, which are expressed at a very low level, with the EF-1alpha genes indicates the existence of a codon bias for highly expressed genes, as has been shown in other organisms.

Site-directed mutants of post-translationally modified sites of yeast eEF1A using a shuttle vector containing a chromogenic switch

Eukaryotic elongation factor 1A (eEF1A, formerly eEF-1 alpha) carries aminoacyl-tRNAs into the A-site of the ribosome in a GTP-dependent manner. In order to probe the structure/function relationships of eEF1A, we have generated site-directed mutants using a modification of a highly versatile yeast shuttle vector, which consists of the insertion of a 66 base long synthetic DNA fragment in the vector's polylinker. Via oligonucleotide-directed mutagenesis, the modification permits the identification of mutant clones based on a chromogenic screen of beta-galactosidase activity. Mutagenesis reactions are performed with two or more oligonucleotides, one introducing the chromogenic shift, and the other(s) introducing the mutation(s) of interest in eEF1A. Several rounds of chromogenic shifts and additional mutations can be performed in succession on the same vector. To address the possible function of the methylated lysines in yeast eEF1A, we have changed the post-translationally modified lysines (residue 30, 79, 316 and 390) to arginines using the above methodology. Yeast with eEF1A mutants that substitute arginine in all four sites do not show any phenotypic change. There is also an apparent equivalency of wild-type and mutant yeast eEF1A in in vitro assays. It is concluded that the post-translational modifications of eEF1A are not of major importance for eEF1A's role in translation.

The first intron of the Arabidopsis thaliana gene coding for elongation factor 1 beta contains an enhancer-like element

Genomic and cDNA clones coding for elongation factor-1 beta (eEF-1 beta) from Arabidopsis thaliana (At) were isolated and characterized. eEF-1 beta was found to be encoded by a single-copy At gene. Chimeric genes fusing the promoter and the 5' untranslated region of the At eEF-1 beta gene to the gus reporter gene were constructed and used to study the expression of this gene in transgenic tobacco plants. Interestingly, it was found that the first intron of this gene is required for high levels of expression. Experiments using chimeric promoters showed that an enhancer-like element is present in the first intron of At eEF-1 beta. Gel-shift assays were used to demonstrate that this intron is specifically bound by putative transcription factors present in nuclear protein extracts.

Gene expression inMucordimorphism

An ongoing dialectic has concerned the relative importance of differential gene expression versus the pattern of new wall deposition in Mucor dimorphism. Numerous physiological processes and enzyme activities have been observed in flux during morphogenesis, but a causal link to dimorphism has been infrequently demonstrated. Very few of the proteins that are conspicuous in two-dimensional polyacrylamide gel electrophoresis are specific to cell morphology or significantly change in amount during morphogenesis. Cyclic AMP, putrescine, S-adenosylmethionine, and enzymes governing their intracellular concentrations show patterns of change that consistently correlate with morphogenesis. The expression of RAS proteins and translation elongation factor-1α activity during morphogenesis are regulated at the level of transcription and post-translational methylation, respectively. Wall chemistry is very similar in both morphologies, but wall deposition is isodiametric in yeasts and vectorial in hyphae. Electron microscopy shows patterns of apparent exocytosis that are generalized in the former and apical in the latter. Research on other dimorphic fungi, including Saccharomyces cerevisiae, suggests an involvement of cytoskeletal proteins and a family of GTP-linked protein kinases in directing polar growth. Some of these elements, which may be controlled quite distal from the genes encoding them, have been demonstrated in Mucor spp., while others are the subject of ongoing investigations. Key words: Mucor, dimorphism, morphogenesis, gene expression, yeasts, hyphae.

Cloning and characterization of a TEF gene for elongation factor 1 alpha from the yeast Arxula adeninivorans

The translation elongation factor EF-1 alpha appears to play a major role in the control of cell proliferation and ageing in higher eukaryotes. Here we report the cloning of the TEF1 gene encoding the elongation factor 1 alpha of the dimorphic yeast Arxula adeninivorans Ls3. The gene is localized on chromosome 2 from Arxula adeninivorans, comprises 1380 bp and encodes a protein containing 459 amino acids. In contrast to other fungi, a second TEF gene encoding an identical, or nearly identical, polypeptide could not be identified. The transcriptional activity of the TEF1 gene did not change during mycelial growth, whereas a slight decrease could be detected during the yeast growth.

Cloning and analysis of cDNA encoding an elongation factor 1 alpha from the dimorphic fungus Histoplasma capsulatum

The cDNA encoding translation elongation factor 1 alpha (EF-1 alpha) was isolated from the dimorphic fungus, Histoplasma capsulatum (Hc), an important pathogen of man. A cDNA library was probed with the tef1 gene from the fungus Mucor racemosus. Ten independent clones were isolated, all with similar restriction patterns. The longest clone (1.96 kb) was sequenced. Southern blot analysis revealed that the Hc tef1 gene was present as a single copy. A single transcript of approx. 2300 nucleotides was found in total RNA from both the yeast and mold forms of the organism. Comparison of the deduced 460-amino-acid Hc EF-1 alpha protein to EF-1 alpha proteins from other species of fungi revealed the greatest degree of similarity to proteins from the filamentous ascomycetes Podospora anserina and Trichoderma reesei. Phylogenetic tree analysis of fungal tef genes indicated that Hc is most closely related to filamentous ascomycetes and most distantly related to the budding yeast Saccharomyces cerevisiae.

Cloning, nucleotide sequence, and expression of tef-1, the gene encoding translation elongation factor 1 alpha (EF-1 alpha) of Neurospora crassa

The tef-1 gene encoding translation elongation factor 1 alpha was cloned from the ascomycete fungus Neurospora crassa. The sequences of genomic DNA and cDNA clones showed that the tef-1 gene contained one ORF of 1380 bp length that is interrupted by three short introns. The deduced polypeptide contained 460 amino acid residues, and the sequence had a high similarity with those of EF-1 alpha polypeptides from other species. The level of tef-1 mRNA was low in conidia but high in growing cells. When mycelia were transferred to poor nutrient media, the level of tef-1 gene mRNA decreased remarkably. The pattern of tef-1 expression was similar to the expression of genes for ribosomal proteins. The tef-1 gene was mapped between arg-3 and leu-4 loci on linkage group I by restriction fragment length polymorphism mapping. Southern blot analysis showed that Neurospora genomic DNA contained only one copy of the tef-1 gene in a genome.

Genetic organization and mRNA expression of enolase genes of Candida albicans

In previous work, we cloned a Candida albicans cDNA for the glycolytic enzyme enolase and found a single, abundant enolase transcript on Northern (RNA) blots and a single protein on immunoblots, using antiserum raised against a recombinant enolase fusion protein. Because C. albicans enolase is abundantly produced during infection and elicits strong host immune responses, the mechanisms regulating enolase production are important for understanding the growth of C. albicans in vivo. To obtain more information on enolase gene expression by C. albicans, we used the enolase cDNA clone to investigate the genetic organization of enolase genes and the steady-state levels of enolase mRNA under several growth conditions. Gene disruption techniques in combination with Southern blot analyses of genomic DNA showed the presence of two enolase gene loci that could be distinguished by the locations of ClaI and Mn/I sites in their 3' flanking regions. Enolase steady-state mRNA levels were greatest during the middle phase of the logarithmic growth curve and were low during stationary phase. Minimal differences in enolase mRNA levels between yeast cells and hyphae were found. Propagation of C. albicans in glucose did not cause increased enolase mRNA levels compared with growth in a nonfermentable carbon source (pyruvate). It was concluded that two gene loci exist for C. albicans enolase and that enolase mRNA is constitutively produced at high levels during active metabolism.

Isolation and characterization of the EF-1 alpha gene of the filamentous fungus Puccinia graminis f. sp. tritici

A gene of Puccinia graminis f. sp. tritici, coding for the translation elongation factor 1 alpha (EF-1 alpha), was isolated from a P. graminis genomic library using the EF-1 alpha gene sequence of Absidia glauca. The coding region of 1389 nucleotides encodes a polypeptide of 463 amino acids and is interrupted by eight introns. An additional intron is located in the 5' untranslated region. A single transcription start point (tsp) was mapped by primer extension. A cDNA fragment corresponding to P. graminis EF-1 alpha mRNA hybridized with a 1.9-kb-long poly(A+)RNA, sufficient to encode the EF-1 alpha protein. Southern hybridization of digested genomic DNA revealed that two copies of the EF-1 alpha gene exist in the genome of P. graminis.

Analysis of the gene for the elongation factor 1 alpha from the zygomycete Absidia glauca. Use of the promoter region for constructions of transformation vectors

The complete genomic DNA sequence was determined for one of the gene for the elongation factor 1 alpha (TEF), isolated from the zygomycete Absidia glauca. Sequence comparison with TEF genes from other fungi show the highest similarity to TEF-genes of the closely related zygomycete Mucor racemosus (Sundstrom et al. 1987). Southern-blot analysis of genomic DNA from A. glauca with the TEF gene reveals six chromosomal copies in the genome. In transformation experiments of A. glauca, vector constructions were used which allow targeting of one of the TEF loci. Several transformants of A. glauca were analyzed at the DNA level. In most cases, rearranged forms of autonomously replicated plasmids could be found in these isolates. However, some transformants show a different restriction pattern of the TEF loci if compared with the parental strains. From Southern-blot data it could be concluded that in one case the rearrangement lies downstream of one TEF locus. In a second case genetic parts following the 3'-end of the TEF gene are moved towards the 5'-end of the gene.

Characterization of yeast EF-1 alpha: non-conservation of post-translational modifications

Elongation factor 1 alpha (EF-1 alpha) is an abundant cellular protein and its amino-acid sequence has been inferred from numerous organisms, including bacteria, archaebacteria, plants and animals. In large measure, it would appear that the overall structure has probably been maintained given the 33% identity and 56% similarity of Escherichia coli EF-Tu with human EF-1 alpha. Chemical sequencing of EF-Tu and EF-1 alpha has revealed that these proteins are post-translationally modified. In order to assess the possible function of these modifications, we have chemically sequenced the EF-1 alpha from the lower eukaryote Saccharomyces cerevisiae (yeast). To our surprise, the methylation pattern of yeast EF-1 alpha was quite different from either rabbit or brine shrimp EF-1 alpha with only the trimethyllysine at position 79 conserved although the yeast protein is 81% identical to rabbit EF-1 alpha. A dimethyllysine was observed at position 316 which corresponds to a trimethyllysine in brine shrimp and rabbit EF-1 alpha. The other positions in yeast EF-1 alpha which were methylated were unrelated to the other six possible positions for modification observed in brine shrimp or rabbit EF-1 alpha. In addition, the unique glyceryl-phosphorylethanolamine observed in mammalian EF-1 alpha and suspected in brine shrimp EF-1 alpha was not found in yeast EF-1 alpha.

Both genes for EF-1 alpha in Candida albicans are translated

In previous work, we showed that Candida albicans has two genes, TEF-1 and TEF-2, which encode identical polypeptides for the highly conserved, essential, protein synthesis factor EF-1 alpha (Breviario et al., 1988). This result prompted questions as to whether C. albicans preferentially uses one of the genes over the other and whether both genes are actually translated into protein. Gene-specific sequence differences in the untranslated portion of each gene made it possible to prepare gene-specific oligonucleotide hybridization probes. Results with the probes showed that the relative steady-state mRNA levels of the two genes were equivalent and that the mRNA for each gene was present in active translation complexes.

Developmental analysis of elongation factor-1 alpha expression in transgenic tobacco

The developmental regulation of the translational elongation factor EF-1 alpha has been analyzed in tobacco. A gene fusion was constructed consisting of the 5' and 3' regions of the tomato genomic clone LeEF-A from the EF-1 alpha gene family and the beta-glucuronidase coding region. Analysis of the transgenic plants containing this chimeric gene demonstrated that the tomato LeEF-A flanking sequences were sufficient to confer expression patterns similar to those of the endogenous tobacco EF-1 alpha gene. The patterns of beta-glucuronidase activity in this system indicated that during plant growth and development EF-1 alpha is regulated with increased expression corresponding to regions of high protein synthesis, including meristems, rapidly growing tissues, and developing gametophytes. In addition, EF-1 alpha expression responds rapidly to changes in growth patterns induced by hormone treatment. Our results are in agreement with studies in animals indicating that EF-1 alpha expression may be rate limiting for protein synthesis and demonstrate that the analysis of EF-1 alpha is of value for studying interrelationships between protein synthesis and developmental control.