Cloning and characterization of the cDNA encoding rice elongation factor 1 beta

Novel biallelic loss of EEF1B2 function links to autosomal recessive intellectual disability

Biallelic variants in EEF1B2 have recently been shown to cause a novel form of non-syndromic intellectual disability (ID) in two unrelated families. More patients are needed to delineate the genotypic and phenotypic spectrum of this gene. In this study, two patients in a family harboring pathogenic compound heterozygous variants in EEF1B2 were identified. They were characterized by non-syndromic ID and fever-sensitive seizures in childhood. Quantitative real-time polymerase chain reaction (QPCR) analysis showed significantly reduced levels of mRNA expression in two patients compared with unaffected controls. The level of EEF1B2 protein was hardly detected in both patients and their unaffected parents. The eef1b2 F0 knockout (crispant) zebrafish presented with abnormal development and light-induced hyperactivity. We identified novel pathogenic EEF1B2 variants within two siblings in a new family. The findings of the expression experiment and first crispant eef1b2 zebrafish model provided further clues to the role of EEF1B2 variants in the pathogenesis of autosomal-recessive ID.

The role of translation elongation factor eEF1 subunits in neurodevelopmental disorders

The multi-subunit eEF1 complex plays a crucial role in de novo protein synthesis. The central functional component of the complex is eEF1A, which occurs as two independently encoded variants with reciprocal expression patterns: whilst eEF1A1 is widely expressed, eEF1A2 is found only in neurons and muscle. Heterozygous mutations in the gene encoding eEF1A2, EEF1A2, have recently been shown to cause epilepsy, autism, and intellectual disability. The remaining subunits of the eEF1 complex, eEF1Bα, eEF1Bδ, eEF1Bγ, and valyl-tRNA synthetase (VARS), together form the GTP exchange factor for eEF1A and are ubiquitously expressed, in keeping with their housekeeping role. However, mutations in the genes encoding these subunits EEF1B2 (eEF1Bα), EEF1D (eEF1Bδ), and VARS (valyl-tRNA synthetase) have also now been identified as causes of neurodevelopmental disorders. In this review, we describe the mutations identified so far in comparison with the degree of normal variation in each gene, and the predicted consequences of the mutations on the functions of the proteins and their isoforms. We discuss the likely effects of the mutations in the context of the role of protein synthesis in neuronal development.

Survey of differentially expressed proteins and genes in jasmonic acid treated rice seedling shoot and root at the proteomics and transcriptomics levels

Two global approaches were applied to develop an inventory of differentially expressed proteins and genes in rice (cv. Nipponbare) seedling grown on Murashige and Skoog medium with and without jasmonic acid (JA). JA significantly reduced the growth of shoot, root, leaf, and leaf sheath depending on JA concentration (1, 2, 5, 10, 25, and 50 microM) as compared with control. Almost 50% growth inhibition of seedling was observed with 5 microM JA. Shoots and roots of seedlings grown on 5 microM JA for 7 days were then used for proteomics and transcriptomics analyses. Two-dimensional gel electrophoresis revealed 66 and 68 differentially expressed protein spots in shoot and root, respectively, compared to their respective controls. Tandem mass spectrometry analysis of these proteins identified 52 (shoot) and 56 (root) nonredundant proteins, belonging to 10 functional categories. Proteins involved in photosynthesis (44%), cellular respiratory (11%), and protein modification and chaperone (11%) were highly represented in shoot, whereas antioxidant system (18%), cellular respiratory (17%), and defense-related proteins (15%) were highly represented in root. Transcriptomics analysis of shoot and root identified 107 and 325 induced genes and 34 and 213 suppressed genes in shoot and root, respectively. Except of unknown genes with over 57% of the total, most genes encode for proteins involved in secondary metabolism, energy production, protein modification and chaperone, transporters, and cytochrome P450. These identified proteins and genes have been discussed with respect to the JA-induced phenotype providing a new insight into the role of JA in rice seedling growth and development.

KEYWORDS

phytohormone * inhibitory concentration * growth * gel-based approach * mass spectrometry * DNA microarray.

eEF1B: At the dawn of the 21st century

Translational regulation of gene expression in eukaryotes can rapidly and accurately control cell activity in response to stimuli or when rapidly dividing. There is increasing evidence for a key role of the elongation step in this process. Elongation factor-1 (eEF1), which is responsible for aminoacyl-tRNA transfer on the ribosome, is comprised of two entities: a G-protein named eEF1A and a nucleotide exchange factor, eEF1B. The multifunctional nature of eEF1A, as well as its oncogenic potential, is currently the subject of a number of studies. Until recently, less work has been done on eEF1B. This review describes the macromolecular complexity of eEF1B, its multiple phosphorylation sites and numerous cellular partners, which lead us to suggest an essential role for the factor in the control of gene expression, particularly during the cell cycle.

Molecular cloning and characterization of the Arabidopsis thaliana alpha-subunit of elongation factor 1B

Using a PCR-based approach, we have isolated two Arabidopsis thaliana cDNA clones (alpha1 and alpha2) encoding the alpha-subunit of translation elongation factor 1B (eEF1Balpha). They encode open reading frames of 228 and 224 amino acids respectively, with extensive homology to eEF1Balpha subunits from different organisms, particularly in the C-terminal half of the protein. They both lack a conserved phosphorylation site that has been implicated in regulating nucleotide exchange activity. Using a plasmid shuffling experiment, we demonstrated that both alpha1 and alpha2 clones are able to complement a mutant yeast strain deficient for the eEF1Balpha subunit. This provides evidence that Arabidopsis encodes at least two functional isoforms of this subunit, termed eEF1Balpha1 and eEF1Balpha2. A third cDNA clone was isolated that appeared to result from an alternative splicing event of the eEF1Balpha1 gene.

The elongation factor-1delta (EF-1delta) originates from gene duplication of an EF-1beta ancestor and fusion with a protein-binding domain

The molecular evolution of two components of elongation factor-1 (EF-1), EF-1beta and EF-1delta was analysed using the distance matrix, the maximum parsimony and the maximum likelihood methods, after careful alignment of protein and cDNA sequences. The topology of the phylogenetic trees obtained supports monophyly of plant EF-1beta and EF-1beta' sequences, and monophyly of higher eukaryotic animal EF-1beta and EF-1delta sequences. EF-1beta and EF-1delta are homologous in their C-terminal domain. EF-1delta, which emerged before arthropods, originates from a beta-type ancestor gene and fusion with a leucine zipper N-terminal motif. Plant EF-1beta and EF-1beta' correspond to paralogous genes whose ancestor was most likely duplicated before the emergence of monocotyledons and dicotyledons.

A novel variant of translation elongation factor-1beta: isolation and characterization of the rice gene encoding EF-1beta2

A rice gene encoding a novel isoform of translation elongation factor-1beta subunit (termed EF-1beta2) was isolated and characterized. The gene comprises of eight exons, and encodes a 226-amino-acid protein. Expression of EF-1beta2 mRNA is abundant in seeds and cultured cells, but is considerably low in the tissues of the rice seedling. Antiserum raised against an EF-1beta2 synthetic peptide detected a protein with a relative molecular mass of about 32 kDa, indicating the EF-1beta2 gene is actually expressed in rice tissues. EF-1beta2 showed a close similarity to the cognate subunits from plant (beta and beta').

Isolation and characterization of a rice cDNA encoding the gamma-subunit of translation elongation factor 1B (eEF1Bgamma)

We isolated a rice cDNA clone (refg) encoding the gamma-subunit of translation elongation factor 1B (eEF-1B gamma; the old designation was EF-1 gamma). The refg encodes an open reading frame of 419 amino acids which shows a similarity to the equivalent sequences from animals and yeast. Complex formation analysis, which showed the recombinant protein of refg (His-eEF1B gamma) and formed a complex with GST-eEF-1Bbeta, indicated that the refg encodes rice eEF1B gamma of the eEF1B alphabeta gamma complex. Expression analysis showed that refg mRNA is very abundant in suspension-cultured cells during the exponential phase of growth. A DNA blot analysis indicated that refg is located at a single locus in the rice genome.

The plant translational apparatus

Protein synthesis in both eukaryotic and prokaryotic cells is a complex process requiring a large number of macromolecules: initiation factors, elongation factors, termination factors, ribosomes, mRNA, amino-acylsynthetases and tRNAs. This review focuses on our current knowledge of protein synthesis in higher plants.

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.

Archaeal elongation factor 1 beta is a dimer. Primary structure, molecular and biochemical properties

The elongation factor 1 beta (EF-1 beta), that in eukarya and archaea promotes the replacement of GDP by GTP on the elongation factor 1 alpha x GDP complex, was purified to homogeneity from the thermoacidophilic archaeon Sulfolobus solfataricus (SsEF-1 beta). Its primary structure was established by sequenced Edman degradation of the entire protein or its proteolytic peptides. The molecular weight of SsEF-1 beta was estimated as about 10000 or 20000 under denaturing or native conditions respectively; this finding suggests that the native protein exists as a dimer. The peptide chain of SsEF-1 beta is much shorter than that of its eukaryotic analogues and homology is found only at their C-terminal region; no homology exists between SsEF-1 beta and eubacterial EF-Ts. At 50 degrees C, at a concentration of SsEF-1 beta 5-fold higher than that of SsEF-1 alpha x [3H]GDP the rate of the exchange of [3H]GDP for GTP becomes about 160-fold faster. An analysis of the values of the energetic parameters indicates that in the presence of SsEF-1 beta the GDP/GTP exchange is entropically favoured. At 100 degrees C the half-life of SsEF-1 beta is about 4 h.

The first nucleotide sequence of an archaeal elongation factor 1 beta gene

An archaeal elongation factor 1 beta gene has been isolated for the first time from a Sulfolobus solfataricus genomic library. The sequenced clone (869 bp) contained two open reading frames, one coding for a protein made of 91 amino acid residues (SsEF-1 beta), the other one encoding a nonidentified product (ORF 115). The amino acid sequences of segments at the N- and C-terminal of the translated SsEF-1 beta were identical to those determined for the native protein. Northern and Southern analyses showed that the SsEF-1 beta gene is represented in S. solfataricus by a unique sequence. Compared to eubacterial or eukaryal corresponding genes the SsEF-1 beta is much shorter.