Untranslated Regions Of Eukaryotic mRNAs Research Articles

UTRdb 2.0: a comprehensive, expert curated catalog of eukaryotic mRNAs untranslated regions.

The 5' and 3' untranslated regions of eukaryotic mRNAs (UTRs) play crucial roles in the post-transcriptional regulation of gene expression through the modulation of nucleo-cytoplasmic mRNA transport, translation efficiency, subcellular localization, and message stability. Since 1996, we have developed and maintained UTRdb, a specialized database of UTR sequences. Here we present UTRdb 2.0, a major update of UTRdb featuring an extensive collection of eukaryotic 5' and 3' UTR sequences, including over 26 million entries from over 6 million genes and 573 species, enriched with a curated set of functional annotations. Annotations include CAGE tags and polyA signals to label the completeness of 5' and 3'UTRs, respectively. In addition, uORFs and IRES are annotated in 5'UTRs as well as experimentally validated miRNA targets in 3'UTRs. Further annotations include evolutionarily conserved blocks, Rfam motifs, ADAR-mediated RNA editing events, and m6A modifications. A web interface allowing a flexible selection and retrieval of specific subsets of UTRs, selected according to a combination of criteria, has been implemented which also provides comprehensive download facilities. UTRdb 2.0 is accessible at http://utrdb.cloud.ba.infn.it/utrdb/.

Translational control by 5'-untranslated regions of eukaryotic mRNAs.

The eukaryotic 5' untranslated region (UTR) is critical for ribosome recruitment to the messenger RNA (mRNA) and start codon choice and plays a major role in the control of translation efficiency and shaping the cellular proteome. The ribosomal initiation complex is assembled on the mRNA via a cap-dependent or cap-independent mechanism. We describe various mechanisms controlling ribosome scanning and initiation codon selection by 5' upstream open reading frames, translation initiation factors, and primary and secondary structures of the 5'UTR, including particular sequence motifs. We also discuss translational control via phosphorylation of eukaryotic initiation factor 2, which is implicated in learning and memory, neurodegenerative diseases, and cancer.

Characterization of the UGA-recoding and SECIS-binding activities of SECIS-binding protein 2

Selenium, a micronutrient, is primarily incorporated into human physiology as selenocysteine (Sec). The 25 Sec-containing proteins in humans are known as selenoproteins. Their synthesis depends on the translational recoding of the UGA stop codon to allow Sec insertion. This requires a stem-loop structure in the 3’ untranslated region of eukaryotic mRNAs known as the Selenocysteine Insertion Sequence (SECIS). The SECIS is recognized by SECIS-binding protein 2 (SBP2) and this RNA:protein interaction is essential for UGA recoding to occur. Genetic mutations cause SBP2 deficiency in humans, resulting in a broad set of symptoms due to differential effects on individual selenoproteins. Progress on understanding the different phenotypes requires developing robust tools to investigate SBP2 structure and function. In this study we demonstrate that SBP2 protein produced by in vitro translation discriminates among SECIS elements in a competitive UGA recoding assay and has a much higher specific activity than bacterially expressed protein. We also show that a purified recombinant protein encompassing amino acids 517-777 of SBP2 binds to SECIS elements with high affinity and selectivity. The affinity of the SBP2:SECIS interaction correlated with the ability of a SECIS to compete for UGA recoding activity in vitro. The identification of a 250 amino acid sequence that mediates specific, selective SECIS-binding will facilitate future structural studies of the SBP2:SECIS complex. Finally, we identify an evolutionarily conserved core cysteine signature in SBP2 sequences from the vertebrate lineage. Mutation of multiple, but not single, cysteines impaired SECIS-binding but did not affect protein localization in cells.

An evolutionary conserved pattern of 18S rRNA sequence complementarity to mRNA 5′ UTRs and its implications for eukaryotic gene translation regulation

There are several key mechanisms regulating eukaryotic gene expression at the level of protein synthesis. Interestingly, the least explored mechanisms of translational control are those that involve the translating ribosome per se, mediated for example via predicted interactions between the ribosomal RNAs (rRNAs) and mRNAs. Here, we took advantage of robustly growing large-scale data sets of mRNA sequences for numerous organisms, solved ribosomal structures and computational power to computationally explore the mRNA–rRNA complementarity that is statistically significant across the species. Our predictions reveal highly specific sequence complementarity of 18S rRNA sequences with mRNA 5′ untranslated regions (UTRs) forming a well-defined 3D pattern on the rRNA sequence of the 40S subunit. Broader evolutionary conservation of this pattern may imply that 5′ UTRs of eukaryotic mRNAs, which have already emerged from the mRNA-binding channel, may contact several complementary spots on 18S rRNA situated near the exit of the mRNA binding channel and on the middle-to-lower body of the solvent-exposed 40S ribosome including its left foot. We discuss physiological significance of this structurally conserved pattern and, in the context of previously published experimental results, propose that it modulates scanning of the 40S subunit through 5′ UTRs of mRNAs.

UTRdb and UTRsite (RELEASE 2010): a collection of sequences and regulatory motifs of the untranslated regions of eukaryotic mRNAs

The 5′ and 3′ untranslated regions of eukaryotic mRNAs (UTRs) play crucial roles in the post-transcriptional regulation of gene expression through the modulation of nucleo-cytoplasmic mRNA transport, translation efficiency, subcellular localization and message stability. UTRdb is a curated database of 5′ and 3′ untranslated sequences of eukaryotic mRNAs, derived from several sources of primary data. Experimentally validated functional motifs are annotated and also collated as the UTRsite database where more specific information on the functional motifs and cross-links to interacting regulatory protein are provided. In the current update, the UTR entries have been organized in a gene-centric structure to better visualize and retrieve 5′ and 3′UTR variants generated by alternative initiation and termination of transcription and alternative splicing. Experimentally validated miRNA targets and conserved sequence elements are also annotated. The integration of UTRdb with genomic data has allowed the implementation of an efficient annotation system and a powerful retrieval resource for the selection and extraction of specific UTR subsets. All internet resources implemented for retrieval and functional analysis of 5′ and 3′ untranslated regions of eukaryotic mRNAs are accessible at http://utrdb.ba.itb.cnr.it/.

Data mining of imperfect double-stranded RNA in [formula omitted] untranslated regions of eukaryotic mRNAs

Recent developments in the study of RNA silencing indicate that double-stranded RNA (dsRNA) can be used in eukaryotes to block expression of a corresponding cellular gene. There is also a large class of small non-coding RNAs having potential to form a distinct, stable stem-loop in numbers of eukaryotic genomes. We had reported that a large imperfect dsRNA structure with hundreds of base-pairs (bp) in the 3 ′ untranslated region ( 3 ′ UTR) of cytotoxic ribonuclease was correlated with the translation suppression. In this study, we search for such dsRNAs in a 3 ′ UTR database. The occurrence rate of large dsRNA in 3 ′ UTRs ranges from 0.01% in plant to 0.30% in vertebrate mRNAs. However, small imperfect dsRNAs of ∼ 30 bp are much more prevalent than large ones. The small dsRNAs are statistically very significant and uniquely well-ordered. Most of them have the conserved structural features of pre-miRNAs. Our data mining of the dsRNAs in the 3 ′ UTR database can be used to explore RNA-based regulation of gene expression.

Protein and RNA Dynamics Play Key Roles in Determining the Specific Recognition of GU-rich Polyadenylation Regulatory Elements by Human Cstf-64 Protein

The N-terminal domain of the 64 kDa subunit of the cleavage stimulation factor (CstF-64) recognizes GU-rich elements within the 3'-untranslated region of eukaryotic mRNAs. This interaction is essential for mRNA 3' end processing and transcription termination, and its strength affects the efficiency of utilization of different polyadenylation sites. The structure of the RNA-binding N-terminal domain of CstF-64 showed how the N-terminal RNA recognition motif of CstF-64 recognizes GU-rich RNAs. However, it is still perplexing how this protein can bind selectively to RNAs that are rich in G and U residues regardless of their detailed sequence composition, yet discriminate effectively against non-GU-RNAs. We investigated by NMR the dynamics of the CstF-64 RNA-binding domain, both free and bound to two GU-rich RNA sequences that represent polyadenylation regulatory elements. While the free protein displays the motional properties typical of a well-folded protein domain and is uniformly rigid, the protein-RNA interface acquires significant mobility on the micro- to millisecond time-scale once GU-rich RNAs binds to it. These motional features, we propose, are intrinsic to the functional requirement to bind all GU-rich sequences and yet to discriminate against non-GU-rich RNAs. This behavior may be a general mechanism by which some RNA-binding proteins are able to bind to classes of sequences, as opposed to a well-defined sequence or consensus.

UTRdb and UTRsite: a collection of sequences and regulatory motifs of the untranslated regions of eukaryotic mRNAs

The 5′ and 3′ untranslated regions of eukaryotic mRNAs play crucial roles in the post-transcriptional regulation of gene expression through the modulation of nucleo-cytoplasmic mRNA transport, translation efficiency, subcellular localization and message stability. UTRdb is a curated database of 5′ and 3′ untranslated sequences of eukaryotic mRNAs, derived from several sources of primary data. Experimentally validated functional motifs are annotated (and also collated as the UTRsite database) and cross-links to genomic and protein data are provided. The integration of UTRdb with genomic and protein data has allowed the implementation of a powerful retrieval resource for the selection and extraction of UTR subsets based on their genomic coordinates and/or features of the protein encoded by the relevant mRNA (e.g. GO term, PFAM domain, etc.). All internet resources implemented for retrieval and functional analysis of 5′ and 3′ untranslated regions of eukaryotic mRNAs are accessible at http://www.ba.itb.cnr.it/UTR/.

Tethered function assays using 3 ′ untranslated regions

Proteins that regulate mRNA metabolism are often bipartite: an RNA binding activity confers substrate specificity, and a “functional” domain elicits the biological outcome. In some cases, these two activities reside on different polypeptides that form a complex on the mRNA. Regardless, experimental separation of RNA binding from function facilitates analysis of both properties, liberating each from the constraints of the other. “Tethered function” assays bring a protein to a reporter RNA through a designed RNA–protein interaction. The function of the tethered protein—whether that be stability, translation, localization, or transport, or otherwise—is then assessed. We refer to this approach as a “tethered function” assay, since it can be examined. The approach does not require knowledge of the natural RNA binding sites, or of the composition of the naturally occurring protein complexes. It can be useful in dissecting how proteins that act on RNAs work, and in identifying active components of multiprotein complexes. RNA-binding proteins previously have been linked to foreign RNA-binding specificities, for a wide variety of purposes. We emphasize here the particular value of tethering to the 3 ′ untranslated region of eukaryotic mRNAs, and the opportunities it presents for the analysis of how those mRNAs are regulated. We discuss experimental design, as well as published and potential applications.

UTRdb and UTRsite: specialized databases of sequences and functional elements of 5' and 3' untranslated regions of eukaryotic mRNAs. Update 2002.

The 5'- and 3'-untranslated regions (5'- and 3'-UTRs) of eukaryotic mRNAs are known to play a crucial role in post-transcriptional regulation of gene expression modulating nucleo-cytoplasmic mRNA transport, translation efficiency, subcellular localization and stability. UTRdb is a specialized database of 5' and 3' untranslated sequences of eukaryotic mRNAs cleaned from redundancy. UTRdb entries are enriched with specialized information not present in the primary databases including the presence of nucleotide sequence patterns already demonstrated by experimental analysis to have some functional role. All these patterns have been collected in the UTRsite database so that it is possible to search any input sequence for the presence of annotated functional motifs. Furthermore, UTRdb entries have been annotated for the presence of repetitive elements. All Internet resources we implemented for retrieval and functional analysis of 5'- and 3'-UTRs of eukaryotic mRNAs are accessible at http://bighost.area.ba.cnr.it/BIG/UTRHome/.

UTRdb and UTRsite: specialized databases of sequences and functional elements of 5' and 3' untranslated regions of eukaryotic mRNAs.

The 5' and 3' untranslated regions of eukaryotic mRNAs may play a crucial role in the regulation of gene expression controlling mRNA localization, stability and translational efficiency. For this reason we developed UTRdb, a specialized database of 5' and 3' untranslated sequences of eukaryotic mRNAs cleaned from redundancy. UTRdb entries are enriched with specialized information not present in the primary databases including the presence of nucleotide sequence patterns already demonstrated by experimental analysis to have some functional role. All these patterns have been collected in the UTRsite database so that it is possible to search any input sequence for the presence of annotated functional motifs. Furthermore, UTRdb entries have been annotated for the presence of repetitive elements. All internet resources implemented for retrieval and functional analysis of 5' and 3' untranslated regions of eukaryotic mRNAs are accessible at http://bigarea.area.ba.cnr.it:8000/EmbIT/UTRH ome/

The untranslated regions of eukaryotic mRNAs: Structure, function, evolution and bioinformatic tools for their analysis

The crucial role of the non-coding portion of genomes is now widely acknowledged. In particular, mRNA untranslated regions are involved in many post-transcriptional regulatory pathways that control mRNA localisation, stability and translation efficiency. A review is given of the most recent research works on the functional characterisation of eukaryotic mRNA untranslated regions. In order to make possible a systematic and detailed sequence analysis of mRNA untranslated regions (UTRs), a non-redundant database of metazoan mRNA untranslated sequences annotated for the occurrence of specific functional elements, UTRdb, was devised. These elements, whose consensus structure has been devised on the basis of experimental assays and of comparative analyses, have been collected in the UTRsite database. A suitable pattern-matching software has been devised to search UTRsite patterns in user-submitted sequences, also assessing their statistical significance. Structural, compositional and evolutionary features of untranslated sequences of metazoan mRNAs have been investigated showing peculiar intra- and interspecific patterns.

Biochemical and Kinetic Characterization of the RNA Helicase Activity of Eukaryotic Initiation Factor 4A

Eukaryotic initiation factor (eIF) 4A is the prototypic member of the DEAD box family of proteins and has been proposed to act as an RNA helicase to unwind secondary structure in the 5'-untranslated region of eukaryotic mRNAs. Previous studies have shown that the RNA helicase activity of eIF4A is dependent on the presence of a second initiation factor, eIF4B. In this report, eIF4A has been demonstrated to function independently of eIF4B as an ATP-dependent RNA helicase. The biochemical and kinetic properties of this activity were examined. By using a family of RNA duplexes with an unstructured single-stranded region followed by a duplex region of increasing length and stability, it was observed that the initial rate of duplex unwinding decreased with increasing stability of the duplex. Furthermore, the maximum amount of duplex unwound also decreased with increasing stability. Results suggest that eIF4A acts in a non-processive manner. eIF4B and eIF4H were shown to stimulate the helicase activity of eIF4A, allowing eIF4A to unwind longer, more stable duplexes with both an increase in initial rate and maximum amount of duplex unwound. A simple kinetic model is proposed to explain the mechanism by which eIF4A unwinds RNA duplex structures in an ATP-dependent manner.

UTRdb: a specialized database of 5' and 3' untranslated regions of eukaryotic mRNAs.

The 5' and 3' untranslated regions of eukaryotic mRNAs may play a crucial role in the regulation of gene expression controlling mRNA localization, stability and translational efficiency. For this reason we developed UTRdb (http://bigarea.area.ba.cnr.it:8000/BioWWW/#U TRdb), a specialized database of 5' and 3' untranslated sequences of eukaryotic mRNAs cleaned from redundancy. UTRdb entries are enriched with specialized information not present in the primary databases including the presence of nucleotide sequence patterns already demonstrated by experimental analysis to have some functional role. All these patterns have been collected in the UTRsite database so that it is possible to search any input sequence for the presence of annotated functional motifs. Furthermore, UTRdb entries have been annotated for the presence of repetitive elements.

The DEAD box protein eIF4A. 1. A minimal kinetic and thermodynamic framework reveals coupled binding of RNA and nucleotide.

eIF4A is the archetypal member of the DEAD box family of proteins and has been proposed to use the energy from ATP hydrolysis to unwind structures in the 5'-untranslated regions of eukaryotic mRNAs during translation initiation. As a step toward understanding the mechanism of action of this class of enzymes, a minimal kinetic and thermodynamic framework for the RNA-activated ATPase function has been established for eIF4A. The enzyme's affinity for ssRNA is modulated by the binding of ATP.Mg2+ and ADP.Mg2+: the affinity of the E.ATP complex for ssRNA is approximately 40-fold higher than that of the E.ADP complex. The enzyme binds its substrates in a random manner; contrary to previous suggestions, neither ATP binding nor hydrolysis is required for binding of single-stranded RNA. The presence or absence of the gamma-phosphate on the bound nucleotide acts as a switch that modulates the enzyme's structure and ssRNA affinity. The data presented in this and the following paper in this issue suggest that ATP binding and hydrolysis produce a cycle of conformational and RNA affinity changes in eIF4A. Such cycles may be used by DEAD box proteins to transduce the energy from ATP hydrolysis into physical work, thereby allowing each member of this family to rearrange its RNA or RNA.protein target.

UTRdb: a specialized database of 5'- and 3'-untranslated regions of eukaryotic mRNAs.

The important role the untranslated regions of eukaryotic mRNAs may play in gene regulation and expression is now widely acknowledged. For this reason we developed UTRdb, a specialized database of 5'- and 3'-untranslated sequences of eukaryotic mRNAs cleaned from redundancy. UTRdb entries are enriched with specialized information not present in the primary databases, including the presence of functional patterns already demonstrated by experimental analysis to have some functional role. A collection of such patterns is being collected in UTRsite database (http://bio-www.ba.cnr.it:8000/srs5/) which can also be used with appropriate computational tools to detect known functional patterns contained in mRNA untranslated regions.

Structural and compositional features of untranslated regions of eukaryotic mRNAs

The important role of 5′ and 3′ untranslated regions of eukaryotic mRNAs in gene regulation and expression is now widely accepted. In order to study the general structural and compositional features of these sequences we developed UTRdb, a specialized database of 5′ and 3′- UTR sequences from seven different taxonomic groups of eukaryotic mRNAs cleaned of redundancy. The analysis of the UTR sequences contained in this database showed that 5′- UTR sequences, on average 200 nucleotides long, are 1.5-3 times shorter than the corresponding 3′- UTR sequences in the various taxonomic groups considered here. As to their compositional properties on average 5′- UTR sequences resulted in all cases GC richer than 3′- UTR sequences, and significant correlations were found between the GC content of 5′ and 3′- UTR sequences and the GC content of the third silent codon positions of the corresponding protein coding genes. The dinucleotide analysis showed a differential depletion of CpG in vertebrate 5′ and 3′- UTR, with 5′- UTR sequences being more CpG-rich, and a generalized depletion of TpA in both 5′ and 3′- UTR was observed in all eukaryotic sequence collections.

MRNA translation: influence of the 5′ and 3′ untranslated regions

Eukaryotic messenger RNA utilization is a tightly controlled process. Control of translation is exerted at several levels, but the predominant step is ribosome binding, which is rate limiting for translation of most mRNAs. There appear to be several alternative modes by which ribosomes bind to the mRNA and initiate translation. Recent data show that both the 5' and 3' untranslated regions of eukaryotic mRNAs play critical roles in mRNA recruitment for translation, and several cis-acting elements have been characterized in detail. In addition, a few trans-acting factors that bind to these elements have been identified. It is possible that the terminal regions of mRNAs interact to enhance translation.

Mutational analysis of a DEAD box RNA helicase: the mammalian translation initiation factor eIF-4A.

eIF-4A is a translation initiation factor that exhibits bidirectional RNA unwinding activity in vitro in the presence of another translation initiation factor, eIF-4B and ATP. This activity is thought to be responsible for the melting of secondary structure in the 5' untranslated region of eukaryotic mRNAs to facilitate ribosome binding. eIF-4A is a member of a fast growing family of proteins termed the DEAD family. These proteins are believed to be RNA helicases, based on the demonstrated in vitro RNA helicase activity of two members (eIF-4A and p68) and their homology in eight amino acid regions. Several related biochemical activities were attributed to eIF-4A: (i) ATP binding, (ii) RNA-dependent ATPase and (iii) RNA helicase. To determine the contribution of the highly conserved regions to these activities, we performed site-directed mutagenesis. First we show that recombinant eIF-4A, together with recombinant eIF-4B, exhibit RNA helicase activity in vitro. Mutations in the ATPase A motif (AXXXXGKT) affect ATP binding, whereas mutations in the predicted ATPase B motif (DEAD) affect ATP hydrolysis. We report here that the DEAD region couples the ATPase with the RNA helicase activity. Furthermore, two other regions, whose functions were unknown, have also been characterized. We report that the first residue in the HRIGRXXR region is involved in ATP hydrolysis and that the SAT region is essential for RNA unwinding. Our results suggest that the highly conserved regions in the DEAD box family are critical for RNA helicase activity.

Pancreas-specific genes: structure and expression.

Via recombinant DNA technology the mRNA sequence of pancreatic amylase has been cloned and its nucleotide sequence has been determined. The cloned sequence represents 96% of the total length of amylase mRNA; missing are an estimated 75 +/- 30 nucleotides from the 5' end. The amino acid sequence of rat pancreatic amylase was deduced solely from the nucleotide sequence of the mRNA. Unlike other eukaryotic mRNAs, the amylase mRNA has short 5' and 5' untranslated regions, suggesting that long untranslated regions of eukaryotic mRNAs either do not contain extensive functional sequences or that these sequences are incorporated within the amino acid coding region of amylase mRNA. The cloned amylase mRNA sequence was radiolabeled and used as a probe for in situ hybridization. These experiments demonstrate that amylase mRNA is present in all acinar cells but not in other pancreatic cell types. Using the cloned amylase mRNA sequences as a hybridization probe, three nonoverlapping genomic DNA fragments containing amylase gene sequences were isolated. From the similar sequence organization of the three amylase genes visualized by DNA heteroduplex mapping, a consensus structure of a rat amylase gene is proposed. It is an extended gene structure 10 kilobase pairs in length containing the 1547 base pairs of the cloned mRNA coding sequence interrupted by seven intervening sequences ranging from 400-2000 base pairs long. Thus, in nuclear DNA the amylase mRNA coding sequence is disrupted into at least eight segments from 150-300 base pairs long.