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Posttranscriptional regulation of insulin-like growth factor II mRNA.

The insulin-like growth factor II (IGF-II) gene generates multiple mature transcripts with different 5' untranslated regions (5'UTR) but identical coding regions and 3'UTRs. We have analysed the translational regulation and decay of the transcripts. Human IGF-II mRNAs provide a provocative example of translational discrimination in which only the minor 4.8 kb mRNA is actively engaged in protein synthesis while the major 6.0 kb mRNA is present in a 100S RNP particle. The 6.0 kb mRNA exhibits a structured 5'UTR of 1170 nucleotides that function as a cis-acting translational attenuator. IGF-II transcripts are processed by endonucleolytic cleavage 1209 and 2183 nucleotides downstream from the translation termination codons in the rat and human, respectively. The cleavage site is situated in a highly conserved and structured domain that exhibits two large hairpins and an intramolecular guanosine quadruplex. The structural elements may provide binding sites for trans-acting factors and ensure that the cleavage site is not sequestered in stable RNA structures. Since expression of IGF-II is initiated from minimal promoters and finished by constitutive secretion from the cell, regulatory events governing IGF-II production are likely to be implemented between the transcriptional and the posttranslational level. The combined effect of translational discrimination and endonucleolysis may therefore play an important role in the regulation of IGF-II expression.

Animals↗

Identification of an alternative open reading frame ("hidden gene"?) stringently required for infectivity of poliovirus cDNA clones.

Translation of the uncapped poliovirus RNA starts at the AUG triplet spanning positions 741-743, and proceeds uninterrupted for almost the entire length of the genome. Such a cap-independent mechanism of internal initiation of translation determines that a long, extra-cistronic region extends between the 5'-end and the main open reading frame (ORF). We have identified 10 short ORFs initiated by the alternative translation initiation codons ACG, AUA, and GUG in the 5'-terminal extra-cistronic region (5'-ECR) of poliovirus RNA. Mutations introduced in all but one of these mini-cistrons had no effect on the infectivity of full-length cDNA clones, except when they modified a "hidden frame" spanning between nucleotides 157-192 (starting triplet: ACG). The mini cistron 157-192 is conserved in position, length and sequence in the genome of all types and strains of poliovirus. Adaptation to rat (Lansing) or mouse (variant of Sabin 2) is accompanied by a consistent pattern of changes in the primary sequence of this "hidden frame". The substitutions that abrogated the infectivity of cDNA clones were not expected to modify the predicted secondary structure of the 5'-ECR, and they did not alter the ability of the IRES to direct internal initiation of translation in bi-cistronic mRNAs. The infectivity of the mutated poliovirus cDNAs could be complemented in trans by co-transfecting the target COS-1 cells with an expression vector containing just the 5'-ECR of poliovirus type 2 (Lansing strain). The infectivity of poliovirus cDNA could be restored by co-transfecting short RNA transcripts of the wt 5'-ECR (Lansing), suggesting that the complementation in trans indeed requires the expression of the helper cDNA clone.

Animals↗

Hepatitis G virus genotypes in Australia, Papua New Guinea and the Solomon Islands: a possible new Pacific type identified.

BACKGROUND: Hepatitis G Virus (HGV)/GB Virus-C (GBV-C) is a newly discovered RNA virus. Nucleotide sequence comparison and phylogenetic studies of the 5' untranslated region (5'UTR) within the viral genome have identified at least three different types which have provisionally been classified as type 1 (West African origin), type 2 (North American origin) and type 3 (Asian origin). METHODS AND RESULTS: The products of RT-PCR were sequenced by using blood donors and patients infected with HGV/GBV-C in Australia, Papua New Guinea and the Solomon Islands to investigate the genotype distribution in this area of the world. All the Australian isolates showed strong sequence homology with type 2, while the Papua New Guinea and Solomon Islands sequences were more closely related, but differ from type 3, which has previously been reported from isolates studied within Asia. CONCLUSIONS: Phylogenetic analysis suggests that these latter sequences are either a new HGV/GBV-C Pacific type or a subtype of the Asian type RNA virus. Isolates homologous with type 1 were not identified in these population groups.

Australia↗

Identification of a target RNA motif for RNA-binding protein HuR.

HuR, a protein that binds to specific mRNA subsets, is increasingly recognized as a pivotal posttranscriptional regulator of gene expression. Here, HuR was immunoprecipitated under conditions that preserved HuR-RNA interactions, and HuR-bound target mRNAs were identified by cDNA array hybridization. Analysis of primary sequences and secondary structures shared among HuR targets led to the identification of a 17- to 20-base-long RNA motif rich in uracils. This HuR motif was found in almost all mRNAs previously reported to be HuR targets, was located preferentially within 3' untranslated regions of all unigene transcripts examined, and was conserved in >50% of human and mouse homologous genes. Importantly, the HuR motif allowed the successful prediction and subsequent validation of novel HuR targets from gene databases. This study describes an HuR target RNA motif and presents a general strategy for identifying target motifs for RNA-binding proteins.

3' Untranslated Regions↗

Comparison of phylogenetic relationships based on phospholipid fatty acid profiles and ribosomal RNA sequence similarities among dissimilatory sulfate-reducing bacteria.

Twenty-five isolates of dissimilatory sulfate-reducing bacteria were clustered based on similarity analysis of their phospholipid ester-linked fatty acids (PLFA). Of these, 22 showed that phylogenetic relationships based on the sequence similarity of their 16S rRNA directly paralleled the PLFA relationships. Desulfobacter latus and Desulfobacter curvatus grouped with the other Desulfobacter spp. by 16S rRNA comparison but not with the PLFA analysis as they contained significantly more monoenoic PLFA than the others. Similarly, Desulfovibrio africanus clustered with the Desulfovibrio spp. by 16S rRNA but not with them when analyzed by PLFA patterns because of higher monoenoic PLFA content. Otherwise, clustering obtained with either analysis was essentially congruent. The relationships defined by PLFA patterns appeared robust to shifts in nutrients and terminal electron acceptors. Additional analyses utilizing the lipopolysaccharide-lipid A hydroxy fatty acid patterns appeared not to shift the relationships based on PLFA significantly except when completely absent, as in Gram-positive bacteria. Phylogenetic relationships between isolates defined by 16S rRNA sequence divergence represent a selection clearly different from the multi-enzyme activities responsible for the PLFA patterns. Determination of bacterial relationships based on different selective pressures for various cellular components provides more clues to evolutionary history leading to a more rational nomenclature.

Desulfovibrio↗

Sequence analysis of low-molecular-weight RNAs by the use of non-radioactive labeling.

A new procedure for non-radioactive labeling of the 3'-terminal -OH was developed to facilitate the sequencing works on low-molecular-weight RNAs. At first, biotinylated pCp (cytidine 3',5'-bisphosphate) was synthesized and ligated to the 3'-terminal of yeast tRNA(Phe) with the aid of RNA ligase. Although the labeling efficiency was high enough, this labeling resulted in a lack of the sequence ladders around the 3'-terminal 10 nucleotides. A longer oligonucleotide, p(dC)(dT)16-Biotin was designed to overcome this defect and proved to be a better non-radioactive 3'-labeling probe.

Biotin↗

Phylogenetic analysis of basidiomycetous yeasts by means of 18S ribosomal RNA sequences: relationship of Erythrobasidium hasegawianum and other basidiomycetous yeast taxa.

The basidiomycetous yeast genus Erythrobasidium Hamamoto, Sugiyama & Komagata, based on the type species E. hasegawianum Hamamoto et al., is characterized by filobasidiaceous basidia and the Q-10 (H2) system as its major ubiquinone. It is tentatively placed in the Filobasidiaceae. The molecular characterization is based on 18S ribosomal RNA sequence comparisons among the basidiomycetous yeasts, and the ultrastructural characterization on the cell wall and hyphal septal pores in E. hasegawianum clearly indicate a close relationship with the teliospore-forming yeasts Rhodosporidium toruloides and Leucosporidium scottii. Our molecular phylogeny with statistical analysis suggests that the existing taxonomic system of basidiomycetous yeasts, based primarily on the morphology of basidia including the teliospores (probasidia), should be revised.

Basidiomycota↗

Amplified DNA in Y1 mouse adrenal tumor cells: isolation of cDNAs complementary to an amplified c-Ki-ras gene and localization of homologous sequences to mouse chromosome 6.

We have isolated cDNA clones complementary to a c-Ki-ras cellular oncogene that is amplified in Y1 mouse adrenal tumor cells, with the amplified sequences located on double-minute chromatin bodies (DMs) and homogeneously staining chromosomal regions (HSRs). Characterization of the cDNAs included the isolation of corresponding genomic clones, Northern blot analysis of RNA, and DNA sequence analysis. Our studies demonstrate that the c-Ki-ras gene amplified in the Y1 cells is homologous to the human c-Ki-ras2 gene. We have also obtained evidence that, in addition to c-Ki-ras, at least one other transcription unit has been amplified in the mouse adrenal tumor cells. Moreover, by Southern blot analysis of Chinese hamster-mouse somatic cell hybrids, we have determined that the amplified DNA sequences associated with DMs and HSRs, including the c-Ki-ras gene, are present in normal mouse cells on chromosome 6.

Adrenal Gland Neoplasms↗

Enhanced sensitivity RNA gel loading buffer that enables efficient RNA separation on native gels.

RNA gel analysis is essential for quality assessment of RNA preparations for subsequent analysis such as microarrays and real-time PCRs. The routinely used standard electrophoresis of RNA through formaldehyde-containing agarose gels is not only labor-intensive and time-consuming, but also involves sizeable quantities of hazardous materials. Above all, it is not sensitive, requiring more than 1 microgram of RNA for the assay. Current gene expression profiling with microarrays and real-time PCR often involves limiting amounts of RNA. It is therefore important to have a more sensitive way to analyze RNA. Here we report an improved ethidium bromide-based RNA gel analysis system with our Superload buffer that increases sensitivity to 12.5 ng of total RNA and allows RNA analysis on a regular native Tris-acetate EDTA (TAE) agarose gel.

Animals↗

A novel method for sequence placement of modified nucleotides in mixtures of transfer RNA.

Sequence placement of post-transcriptionally modified nucleosides in tRNA can be experimentally difficult, particularly in cases involving new or unexpected modifications or sequence sites. We describe a mass spectrometry-based approach to this problem, involving the following steps: crude isolations of one or several tRNAs by HPLC from an unfractionated tRNA mixture; digestion to oligonucleotide mixtures by RNase T1; analysis by combined HPLC/electrospray ionization-MS for recognition of modifications; and direct gas-phase sequencing of selected targets in the mixture by LC/MS/MS. Isoacceptor identity can be established in favorable cases when tRNA gene sequences are available.

Chromatography, High Pressure Liquid↗

Prenatal diagnosis and a donor splice site mutation in fibrillin in a family with Marfan syndrome.

The Marfan syndrome, an autosomal dominant connective tissue disorder, is manifested by abnormalities in the cardiovascular, skeletal, and ocular systems. Recently, fibrillin, an elastin-associated microfibrillar glycoprotein, has been linked to the Marfan syndrome, and fibrillin mutations in affected individuals have been documented. In this study, genetic linkage analysis with fibrillin specific markers was used to establish the prenatal diagnosis in an 11-wk-gestation fetus in a four-generation Marfan kindred. At birth, skeletal changes suggestive of the Marfan syndrome were observed. Reverse transcription-PCR amplification of the fibrillin gene mRNA detected a deletion of 123 bp in one allele in affected relatives. This deletion corresponds to an exon encoding an epidermal growth factor-like motif. Examination of genomic DNA showed a G-->C transversion at the +1 consensus donor splice site.

Adult↗

Genetic variability of genomic RNA 2 of four tobacco rattle tobravirus isolates from potato fields in the Northwestern United States.

Sequence analysis of RNA 2 of four Tobacco rattle virus (TRV) isolates collected from potato fields in Oregon (OR2, Umt1), Washington (BM), and Colorado (Cot2) revealed significant homologies to the ORY isolate from North America. Phylogenetic analysis based on a comparison of nucleotide (nt) and amino acid (aa) sequences with other members of the genus Tobravirus indicates that the North American isolates cluster as a distinct group. All of the RNAs are predicted to contain open reading frames (ORFs) potentially encoding the coat protein (CP, ORF 2a) and 37.6 kDa (ORF 2b) ORFs. In addition, they all contain a region of similarity to the 3' terminus of RNA 1 of ORY, including a truncated portion of the 16 kDa cistron from the 3' end of RNA 1. Three of the isolates, which are nematode transmissible, OR2, BM, and Cot2, also contain a third putative ORF (ORF 2c) which encodes a protein of 33.6 kDa. The fourth isolate, Umt1, which is not nematode transmissible, is the most divergent of the isolates as it encodes a truncated version of ORF 2c. The ORF 2c deletion in Umt1 may contribute to its inability to be transmitted by the vector. The results reported in this article indicate again that the TRV genome is flexible. Interestingly, although both isolates Umt1 and Cot2 were mechanically transmitted to tobacco from potato, only Umt1 exhibits the deletion in RNA 2. TRV Isolate Umt1, therefore, appears to be another example of rapid adaptation of the TRV genome to non-field conditions.

Animals↗

Evolution of bacteriophage in continuous culture: a model system to test antiviral gene therapies for the emergence of phage escape mutants.

The emergence of viral escape mutants is usually a highly undesirable phenomenon. This phenomenon is frequently observed in antiviral drug applications for the treatment of viral infections and can undermine long-term therapeutic success. Here, we propose a strategy for evaluating a given antiviral approach in terms of its potential to provoke the appearance of resistant virus mutants. By use of Q beta RNA phage as a model system, the effect of an antiviral gene therapy, i.e., a virus-specific repressor protein expressed by a recombinant Escherichia coli host, was studied over the course of more than 100 generations. In 13 experiments carried out in parallel, 12 phage populations became resistant and 1 became extinct. Sequence analysis revealed that only two distinct phage mutants emerged in the 12 surviving phage populations. For both escape mutants, sequence variations located in the repressor binding site of the viral genomic RNA, which decrease affinity for the repressor protein, conferred resistance to translational repression. The results clearly suggest the feasibility of the proposed strategy for the evaluation of antiviral approaches in terms of their potential to allow resistant mutants to appear. In addition, the strategy proved to be a valuable tool for observing virus-specific molecular targets under the impact of antiviral drugs.

Allolevivirus↗

RESCUE-ESE identifies candidate exonic splicing enhancers in vertebrate exons.

A typical gene contains two levels of information: a sequence that encodes a particular protein and a host of other signals that are necessary for the correct expression of the transcript. While much attention has been focused on the effects of sequence variation on the amino acid sequence, variations that disrupt gene processing signals can dramatically impact gene function. A variation that disrupts an exonic splicing enhancer (ESE), for example, could cause exon skipping which would result in the exclusion of an entire exon from the mRNA transcript. RESCUE-ESE, a computational approach used in conjunction with experimental validation, previously identified 238 candidate ESE hexamers in human genes. The RESCUE-ESE method has recently been implemented in three additional species: mouse, zebrafish and pufferfish. Here we describe an online ESE analysis tool (http://genes.mit.edu/burgelab/rescue-ese/) that annotates RESCUE-ESE hexamers in vertebrate exons and can be used to predict splicing phenotypes by identifying sequence changes that disrupt or alter predicted ESEs.

Animals↗

Alkali myosin light chains in man are encoded by a multigene family that includes the adult skeletal muscle, the embryonic or atrial, and nonsarcomeric isoforms.

A set of cDNA clones coding for alkali myosin light chains (AMLC) was isolated from fetal human skeletal muscle. Nucleotide sequence analysis and RNA expression patterns of individual clones revealed related sequences corresponding to (i) fast fiber type MLC1 and MLC3; (ii) the embryonic MLC that is also expressed in fetal ventricle and adult atrium (MLCemb); and (iii) a nonsarcomeric MLC isoform that is found in all nonmuscle cell types and smooth muscle. The AMLC gene family in man comprises unique copies for MLC1, MLC3 and MLCemb, and multiple copies for the nonsarcomeric MLC genes. The gene coding for MLC1 and MLC3 is located on human chromosome 2.

Amino Acid Sequence↗

Generation of EST and microarray resources for functional genomic studies on chicken intestinal health.

Expressed sequenced tags (ESTs) and microarray resources have a great impact on the ability to study host response in mice and humans. Unfortunately, these resources are not yet available for domestic farm animals. The aim of this study was to provide genomic resources to study chicken intestinal health, in particular malabsorption syndrome (MAS), which affects mainly the intestine. Therefore a normalized and subtracted cDNA library containing more than 7000 clones was prepared. Randomly chosen clones were sequenced for control purposes. New ESTs were found and multiple ESTs not identified in the chicken intestine before were observed. The number of non-specific ESTs in this cDNA library was low. Based on this normalized and subtracted library a cDNA microarray was made. In a preliminary hybridization experiment with the microarray, genes were identified to be up- or downregulated in MAS infected chickens. This indicates that the generated resources are valuable tools to investigate chicken intestinal health by whole genome expression analysis approaches.

Animals↗

Molecular cloning and characterization of a Sendai virus internal deletion defective RNA.

A small defective Sendai virus RNA was selectively amplified from a virus preparation obtained after serial undiluted passages in embryonated eggs. Preliminary characterization showed that this defective RNA was a true internal deletion defective RNA, containing the 5' and 3' ends of the non-defective viral genomic RNA. Cloning of this RNA after reverse transcription and polymerase chain reaction amplification was performed in such a way that an exact copy of the defective RNA could be obtained by transcription of the plasmid with T7 RNA polymerase. Sequence analysis of the plasmid allowed further characterization of the defective RNA. It was shown potentially to encode a C-terminally truncated nucleocapsid (NP) protein of 162 amino acids. This truncated NP protein was identified in cells naturally infected with the defective virus preparation. Moreover the protein produced was shown to correspond to the protein synthesized in vitro from the T7 polymerase transcript of the cloned defective genome.

Base Sequence↗

Structural analysis of aligned RNAs.

The knowledge about classes of non-coding RNAs (ncRNAs) is growing very fast and it is mainly the structure which is the common characteristic property shared by members of the same class. For correct characterization of such classes it is therefore of great importance to analyse the structural features in great detail. In this manuscript I present RNAlishapes which combines various secondary structure analysis methods, such as suboptimal folding and shape abstraction, with a comparative approach known as RNA alignment folding. RNAlishapes makes use of an extended thermodynamic model and covariance scoring, which allows to reward covariation of paired bases. Applying the algorithm to a set of bacterial trp-operon leaders using shape abstraction it was able to identify the two alternating conformations of this attenuator. Besides providing in-depth analysis methods for aligned RNAs, the tool also shows a fairly well prediction accuracy. Therefore, RNAlishapes provides the community with a powerful tool for structural analysis of classes of RNAs and is also a reasonable method for consensus structure prediction based on sequence alignments. RNAlishapes is available for online use and download at http://rna.cyanolab.de.

5' Untranslated Regions↗