Biomedical subjects

J V Maizel

Publications and source records attributed to J V Maizel.

At least 19 recordsLinked to original sources

PubMed1997

A common RNA structural motif involved in the internal initiation of translation of cellular mRNAs.

The 5'-non-translated regions (5'NTR) of human immunoglobulin heavy chain binding protein (BiP), Antennapedia (Antp) ofDrosophilaand human fibroblast growth factor 2 (FGF-2) mRNAs are reported to mediate translation initiation by an internal ribosome binding mechanism. In this study, we investigate predicted features of the higher order structures folded in these 5'NTR sequences. Statistical analyses of RNA folding detected a 92 nt unusual folding region (UFR) from 129 to 220, close to the initiator AUG in the BiP mRNA. Details of the structural analyses show that the UFR forms a Y-type stem-loop structure with an additional stem-loop in the 3'-end resembling the common structure core found in the internal ribosome entry site (IRES) elements of picornavirus. The Y-type structural motif is also conserved among a number of divergent BiP mRNAs. We also find two RNA elements in the 5'-leader sequence of human FGF-2. The first RNA element (96 nt) is 2 nt upstream of the first CUG start codon located in the reported IRES element of human FGF-2. The second (107 nt) is immediately upstream of the authentic initiator AUG of the main open reading frame. Intriguingly, the folded RNA structural motif in the two RNA elements is conserved in other members of FGF family and shares the same structural features as that found in the 5'NTR of divergent BiP mRNAs. We suggest that the common RNA structural motif conserved in the diverse BiP and FGF-2 mRNAs has a general function in the internal ribosome binding mechanism of cellular mRNAs.

Antennapedia Homeodomain Protein↗

PubMed1996

A common structural core in the internal ribosome entry sites of picornavirus, hepatitis C virus, and pestivirus.

Cap-independent translations of viral RNAs of enteroviruses and rhinoviruses, cardioviruses and aphthoviruses, hepatitis A and C viruses (HAV and HCV), and pestivirus are initiated by the direct binding of 40S ribosomal subunits to a cis-acting genetic element termed the internal ribosome entry site (IRES) or ribosome landing pad (RLP) in the 5' noncoding region (5'NCR). RNA higher ordered structure models for these IRES elements were derived by a combined approach using thermodynamic RNA folding, Monte Carlo simulation, and phylogenetic comparative analysis. The structural differences among the three groups of picornaviruses arise not only from point mutations, but also from the addition or deletion of structural domains. However, a common core can be identified in the proposed structural models of these IRES elements from enteroviruses and rhinoviruses, cardioviruses and aphthoviruses, and HAV. The common structural core identified within the picornavirus IRES is also conserved in the 5'NCR of the divergent viruses, HCV, and pestiviruses. Furthermore, the proposed structural motif shares a structural feature similar to that observed in the catalytic core of the group 1 intron. The conserved structural motif from these divergent sequences that looks like the common core region of group 1 introns is probably a crucial element involved in the IRES-dependent translation.

Animals↗

PubMed1995

Unusual folding regions and ribosome landing pad within hepatitis C virus and pestivirus RNAs.

A statistically significant folding region is identified in the 5' untranslated region (5'-UTR) of hepatitis C virus (HCV), bovine viral diarrhea virus and hog cholera virus. This unusual folding region (UFR) detected in HCV encompasses 199 nucleotides (nt) and coincides with the reported internal ribosome entry site or ribosome landing pad (RLP), as determined by the 5' and 3' deletions [Tsukiyama-Kohara et al., J. Virol. 66 (1992) 1476-1483]. The RNA structure predicted in the UFR of HCV consists of a large stem-loop and a pseudoknot. The proposed structural model is consistent with RNase sensitivity studies [Brown et al., Nucleic Acids Res. 20 (1992) 5041-5045]. Moreover, the structure is highly conserved among these divergent HCV and pestivirus RNAs. The covariation of paired bases in the helical regions offers support for the proposed structural models. The pseudoknot predicted in these UFR shares a similar structural feature to those proposed in the RLP of cardioviruses, aphthoviruses and hepatitis A virus. Based on the common structural motif, a putative base-pairing model between HCV RNA and 18S rRNA, as well as pestiviral RNAs and 18S rRNA are suggested. Intriguingly, the proposed base-pairing models in this study are comparable to those proposed in picornaviruses in terms of their folded shape and location of the predicted complementary sequences between viral RNAs and 18S rRNA. Taken together, we suggest that the common base-pairing model between the UFR detected in the 5'-UTR of pestivirus and HCV and 18S rRNA have a general function in the internal initiation of cap-independent translation.

Base Sequence↗

PubMed1995

A method for predicting common structures of homologous RNAs.

We have developed a procedure, composed of a set of computer programs, for predicting common RNA structures of homologous sequences. Given a set of homologous RNAs, these programs perform a multiple sequence alignment, generate a list of possible helical stems that are thermodynamically favored in RNA folding from a selected individual sequence, establish a conserved stem list by inspecting the equivalent base pairings and/or conserved helical stems from the derived alignment of homologous RNAs, and build common RNA secondary structures with the maximum scores (i.e., compensatory base changes and number of base pairs, etc.). The approach is a combination of phylogenetic and thermodynamic methods and has been applied to the prediction of common folding structures of the 5' untranslated regions in a number of positive RNA viruses.

Algorithms↗

PubMed1994

RNA tertiary structure of the HIV RRE domain II containing non-Watson-Crick base pairs GG and GA: molecular modeling studies.

We have used molecular modeling techniques to model the RNA tertiary structure of the viral RNA element (referred to as domain II of Rev responsive element, RRE) bound by the Rev protein of HIV. In this study, the initial three-dimensional model was built from its established RNA secondary structure, including three non-Watson-Crick G:G, G:A and G:U base pairs. Molecular dynamics (MD) simulations were performed with hydrated or unhydrated sodium ions. Our results indicate that the non-Watson-Crick base pairs in the simulation with unhydrated sodium ions and water are more stable than those with hydrated sodium ions only. The RNA can maintain its compact double helical structure throughout the course of the MD simulations with water and unhydrated sodium ions, although the non-Watson-Crick base pairs and two bulge loops show much more flexibility and conformational distortion than the classical RNA helical region. The distinct distortion of the sugar-phosphate backbone significantly widens the RNA major groove so that the major groove is readily accessible for hydrogen bonding by specific Rev binding. This model emphasizes the importance of specific hydrogen bonding in the stabilization of the three-dimensional structure of the HIV Rev core binding element, not only between the nucleotide bases, but also among the ribose hydroxyls, phosphate anionic oxygens, base oxygens and nitrogens, and bridging water molecules. Moreover, our results suggest that sodium ions play an important role in the formation of base pairs G:G and G:A of the RRE by a manner similar to the arginine of the Rev-RRE complex.

Adenine↗

PubMed1994

Distinct structural elements and internal entry of ribosomes in mRNA3 encoded by infectious bronchitis virus.

Infectious bronchitis virus (IBV) mRNA3 encodes three small proteins, 3a, 3b, and 3c, at its 5' end. Recently, it was demonstrated that initiation of protein 3c is dependent on the upstream sequence. Monte Carlo simulations of RNA folding in this tricistronic mRNA3 indicate that a highly significant folding region occurs prior to the initiator AUG of 3c. The unusual folding region (UFR) of 265 nucleotides (nt) contains the coding sequences of proteins 3a and 3b. Details of the structural analyses show that five highly significant RNA stem-loops in the UFR can be modeled into a compact superstructure by the interaction of two predicted pseudoknot structures. The folded superstructure comprising nt 44 to 330, with additional 22 nt downstream from this UFR, is suggested to serve as a ribosome landing pad (or an internal ribosomal entry site) in the cap-independent translation of the 3c of IBV. Intriguingly, the proposed structural motif of this coronavirus shares structural features similar to those proposed in a number of picornavirus mRNAs. Based on the common structural features, a plausible base pairing model between mRNA3 and 18 S rRNA is suggested, which is consistent with a general mechanism for regulation of internal initiation described in many picornaviruses.

Base Sequence↗

PubMed1993

Conserved tertiary structural elements in the 5' nontranslated region of cardiovirus, aphthovirus and hepatitis A virus RNAs.

Statistical analyses of RNA folding in 5' nontranslated regions (5'NTR) of encephalomyocarditis virus, Theiler's murine encephalomyelitis virus, foot-and-mouth disease virus, and hepatitis A virus indicate that two highly significant folding regions occur in the 5' and 3' portions of the 5'NTR. The conserved tertiary structural elements are predicted in the unusual folding regions (UFR) for these viral RNAs. The theoretical, common structural elements predicted in the 3' parts of the 5'NTR occur in a cis-acting element that is critical for internal ribosome binding. These structural motifs are expected to be highly significant from extensive Monte Carlo simulations. Nucleotides (nt) in the conserved single-stranded polypyrimidine tract for these RNAs are involved in a distinctively tertiary interaction that is located at about 15 nt prior to the initiator AUG. Intriguingly, the proposed common tertiary structure in this study shares a similar structural feature to that proposed in human enteroviruses and rhinoviruses. Based on these common structural features, plausible base pairing models between these viral RNAs and 18 S rRNA are suggested, which are consistent with a general mechanism for regulation of internal initiation of cap-independent translation.

Aphthovirus↗

PubMed1993

Prediction of alternative RNA secondary structures based on fluctuating thermodynamic parameters.

In this paper we present a new method for predicting a set of RNA secondary structures that are thermodynamically favored in RNA folding simulations. This method uses a large number of 'simulated energy rules' (SER) generated by perturbing the free energy parameters derived experimentally within the range of the experimental errors. The structure with the lowest free energy is computed for each SER. Structural comparisons are used to avoid multiple generation of similar structures. Computed structures are evaluated using the energy distribution of the lowest free energy structures derived in the simulation. Predicted be graphically displayed with their occurring frequencies in the simulation by dot-plot representations. On average, about 90% of phylogenetic helixes in the known models of tRNA, Group I self-splicing intron, and Escherichia coli 16 S rRNA, were predicted using the method.

Algorithms↗

PubMed1993

Identification of unusual RNA folding patterns encoded by bacteriophage T4 gene 60.

A 50-nucleotide (nt) untranslated region (coding gap sequence) that interrupts the amino acid coding sequence in T4 gene 60, plus an additional 5 nt upstream and another 3 nt downstream from the gap sequence, shows unusual folding patterns according to RNA structure prediction. A predicted highly stable and significant hairpin structure in the 5' half of the gap sequence and a plausible tertiary structural element computed in the 3' part of the gap sequence seem significant by statistical tests on the wild-type (wt) sequence. This feature is absent in insertion, deletion and substitution variants of the gap sequence, in which template activities are markedly lower than that of the wt. The proposed feature is consistent with currently available data showing that the translational bypass of the coding gap is correlated with a stop codon involved in a stem-loop structure folded in the gap sequence. We suggest that the role of this segment in 'ribosomal bypass' of a portion of the mRNA sequence is a property of its special folded structure.

Bacteriophage T4↗

PubMed1992

Conserved tertiary structure elements in the 5' untranslated region of human enteroviruses and rhinoviruses.

A combination of comparative sequence analysis and thermodynamic methods reveals the conservation of tertiary structure elements in the 5' untranslated region (UTR) of human enteroviruses and rhinoviruses. The predicted common structural elements occur in the 3' end of a segment that is critical for internal ribosome binding, termed "ribosome landing pad" (RLP), of polioviruses. Base pairings between highly conserved 17-nucleotide (nt) and 21-nt sequences in the 5' UTR of human enteroviruses and rhinoviruses constitute a predicted pseudoknot that is significantly more stable than those that can be formed from a large set of randomly shuffled sequences. A conserved single-stranded polypyrimidine tract is located between two conserved tertiary elements. R. Nicholson, J. Pelletier, S.-Y. Le, and N. Sonenberg (1991, J. Virol. 65, 5886-5894) demonstrated that the point mutations of 3-nt UUU out of an essential 4-nt pyrimidine stretch sequence UUUC abolished translation. Structural analysis of the mutant sequence indicates that small point mutations within the short polypyrimidine sequence would destroy the tertiary interaction in the predicted, highly ordered structure. The proposed common tertiary structure can offer experimentalists a model upon which to extend the interpretations for currently available data. Based on these structural features possible base-pairing models between human enteroviruses and 18 S rRNA and between human rhinoviruses and 18 S rRNA are proposed. The proposed common structure implicates a biological function for these sequences in translational initiation.

Base Composition↗

PubMed1992

A procedure for RNA pseudoknot prediction.

The RNA pseudoknot has been proposed as a significant structural motif in a wide range of biological processes of RNAs. A pseudoknot involves intramolecular pairing of bases in a hairpin loop with bases outside the stem of the loop to form a second stem and loop region. In this study, we propose a method for searching and predicting pseudoknots that are likely to have functional meaning. In our procedure, the orthodox hairpin structure involved in the pseudoknot is required to be both statistically significant and relatively stable to the others in the sequence. The bases outside the stem of the hairpin loop in the predicted pseudoknot are not entangled with any formation of a highly stable secondary structure in the sequence. Also, the predicted pseudoknot is significantly more stable than those that can be formed from a large set of scrambled sequences under the assumption that the energy contribution from a pseudoknot is proportional to the size of second loop region and planar energy contribution from second stem region. A number of functional pseudoknots that have been reported before can be identified and predicted from their sequences by our method.

Algorithms↗

PubMed1992

Extensive sequence-specific information throughout the CAR/RRE, the target sequence of the human immunodeficiency virus type 1 Rev protein.

The significance and location of sequence-specific information in the CAR/RRE, the target sequence for the Rev protein of the human immunodeficiency virus type 1 (HIV-1), have been controversial. We present here a comprehensive experimental and computational approach combining mutational analysis, phylogenetic comparison, and thermodynamic structure calculations with a systematic strategy for distinguishing sequence-specific information from secondary structural information. A target sequence analog was designed to have a secondary structure identical to that of the wild type but a sequence that differs from that of the wild type at every position. This analog was inactive. By exchanging fragments between the wild-type sequence and the inactive analog, we were able to detect an unexpectedly extensive distribution of sequence specificity throughout the CAR/RRE. The analysis enabled us to identify a critically important sequence-specific region, region IIb in the Rev-binding domain, strongly supports a proposed base-pairing interaction in this location, and places forceful constraints on mechanisms of Rev action. The generalized approach presented can be applied to other systems.

Base Sequence↗

PubMed1992

Novel GACG-hairpin pair motif in the 5' untranslated region of type C retroviruses related to murine leukemia virus.

We searched for the presence of common RNA structural motifs in mammalian type C retroviruses related to murine leukemia viruses and the closely related avian spleen necrosis virus. A novel motif consisting of a pair of hairpins, called hairpin pair motif, was detected in the 5' untranslated regions of the genomes of these retroviruses. A combination of computational analyses that included the assessment of phylogenetic sequence conservation by multiple alignment, the search for regions with unusual RNA folding properties, and the analysis of RNA secondary structure by suboptimal free-energy calculations highlighted the significance of this hairpin pair motif. The hairpin pair motif encompasses 70 to 80 nucleotides between the splice donor site and the gag translational initiation codon of these viruses. The motif is composed of two adjacent hairpins both with a perfectly conserved GACG tetraloop. We propose that the novel GACG-hairpin pair motif described here constitutes an essential component of the regulatory machinery in these type C retroviruses.

Base Sequence↗

PubMed1991

RNA pseudoknots downstream of the frameshift sites of retroviruses.

RNA pseudoknot structural motifs could have implications for a wide range of biological processes of RNAs. In this study, the potential RNA pseudoknots just downstream from the known and suspected retroviral frame-shift sites were predicted in the Rous sarcoma virus, primate immunodeficiency viruses (HIV-1, HIV-2, and SIV), equine infectious anemia virus, visna virus, bovine leukemia virus, human T-cell leukemia virus (types I and II), mouse mammary tumor virus, Mason-Pfizer monkey virus, and simian SRV-1 type-D retrovirus. Also, the putative RNA pseudoknots were detected in the gag-pol overlaps of two retrotransposons of Drosophila, 17.6 and gypsy, and the mouse intracisternal A particle. For each sequence, the thermodynamic stability and statistical significance of the secondary structure involved in the predicted tertiary structure were assessed and compared. Our results show that the stem-loop structures in the pseudoknots are both thermodynamically highly stable and statistically significant relative to other such configurations that potentially occur in the gag-pol or gag-pro and pro-pol junction domains of these viruses (300 nucleotides upstream and downstream from the possible frameshift sites are included). Moreover, the structural features of the predicted pseudoknots following the frameshift site of pro-pol overlaps of the HTLV-1 and HTLV-2 retroviruses are structurally well conserved. The occurrence of eight compensatory base changes in the tertiary interaction of the two related sequences allow the conservation of their tertiary structures in spite of the sequence divergence. The results support the possible control mechanism for frameshifting proposed by Brierley et al. and Jacks et al.

Base Sequence↗

PubMed1991

Detection of unusual RNA folding regions in HIV and SIV sequences.

We have developed a method for detecting more stable and significant folding regions relative to others in the sequence. The algorithm is based on the calculation of the lowest free energy of RNA secondary structures and Monte Carlo simulation. For any given RNA segment, the stability and statistical significance of RNA folding are assessed by two measures: the stability score and the significance score. The stability score measures the degree of thermodynamic stability of the segment between all possible biological segments in the RNA sequence. The significance score characterizes the specific arrangement of the nucleotides in the segment that could imply a structural role for the sequence information. Using these two measures, we are able to detect a series of distinct folding regions where highly stable and statistically significant secondary structures occur in human immunodeficiency virus (HIV) and simian immunodeficiency virus (SIV) sequences.

Algorithms↗

PubMed1990

A highly conserved RNA folding region coincident with the Rev response element of primate immunodeficiency viruses.

A series of unusual folding regions (UFR) immediately 3' to the cleavage site of the outer membrane protein (OMP) and transmembrane protein (TMP) were detected in the envelope gene RNA of the human immunodeficiency virus (HIV-1, HIV-2) and simian immunodeficiency virus (SIV) by an extensive Monte Carlo simulation. These RNA secondary structures were predicted to be both highly stable and statistically significant. In the calculation, twenty-five different sequence isolates of HIV-1, three isolates of HIV-2 and eight sequences of SIV were included. Although significant sequence divergence occurs in the env coding regions of these viruses, a distinct UFR of 234-nt is consistently located ten nucleotides 3' to the cleavage site of the OMP/TMP in HIV-1, and a 216-nt UFR occurs forty-six and forty-nine nucleotides downstream from the OMP/TMP cleavage site of HIV-2 and SIV, respectively. Compensatory base changes in the helical stem regions of these conserved RNA secondary structures are identified. These results support the hypothesis that these special RNA folding regions are functionally important and suggest that the role of this sequence as the Rev response element (RRE) is mediated by secondary structure as well as primary RNA sequence.

Base Sequence↗

PubMed1990

Speeding up the dynamic algorithm for planar RNA folding.

The simplest dynamic algorithm for planar RNA folding searches for the maximum number of base pairs. The algorithm uses O(n3) steps. The more general case, where different weights (energies) are assigned to stacked base pairs and to the various types of single-stranded region topologies, requires a considerably longer computation time because of the partial backtracking involved. Limiting the loop size reduces the running time back to O(n3). Reduction in the number of steps in the calculations of the various RNA topologies has recently been suggested, thereby improving the time behavior. Here we show how a "jumping" procedure can be used to speed up the computation, not only for the maximal number of base pairs algorithm, but for the minimal energy algorithm as well.

Algorithms↗

PubMed1990

Localization and molecular modelling of the membrane-inserted domain of the ninth component of human complement and perforin.

Upon interaction with the membrane-bound C5b-8 complex, the ninth component of complement (C9) unfolds and inserts into the membrane of cells on which surface complement has been activated. Consequently C9 oligomerization occurs and transmembrane channels of varying sizes are formed. The domain of the unfolded protein interacting with the cell membrane has so far not been identified since, unlike many integral membrane proteins, the C9 sequence does not contain a continuous stretch of hydrophobic amino acids. We studied the interaction of C9 with the lipid bilayer using the membrane-restricted photoaffinity label 3-(trifluoromethyl)-3-(m[125I]iodophenyl)diazirine (125I-TID). C9 was assembled on liposomes and after photoactivation, several labeled and non-labeled peptides, obtained by chemical and enzymatic cleavage or the 125I-TID-labeled C9, were analyzed. The segment from 176 to 345 was identified as the region containing the membrane-interacting structure. By means of secondary structure predictions, we identified two amphipathic alpha-helices (292-308 and 313-333) separated by a turn (309-312). Based on these results, we constructed a molecular model for the membrane-spanning region of C9. By analogy, we also constructed a model for this domain in perforin/cytolysin, a pore-forming protein found in the cytoplasmic granules of cytotoxic T-lymphocytes.

Affinity Labels↗