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At least 1,009 records · Page 56Linked to original sources
PubMed1990

Sequence of the genome RNA of rubella virus: evidence for genetic rearrangement during togavirus evolution.

The nucleotide sequence of the rubella virus (RUB) genomic RNA was determined. The RUB genomic RNA is 9757 nucleotides in length [excluding the poly(A) tail] and has a G/C content of 69.5%, the highest of any RNA virus sequenced to data. The RUB genomic RNA contains two long open reading frames (ORFs), a 5'-proximal ORF of 6656 nucleotides and a 3'-proximal ORF of 3189 nucleotides which encodes the structural proteins. Thus, the genomic organization of RUB is similar to that of alphaviruses, the other genus of the Togavirus family, and the 5'-proximal ORF of RUB therefore putatively codes for the nonstructural proteins. Sequences homologous to three regions of nucleotide sequence highly conserved among alphaviruses (a stem-and-loop structure at the 5' end of the genome, a 51-nucleotide conserved sequence near the 5' end of the genome, and a 20-nucleotide conserved sequence at the subgenomic RNA start site) were found in the RUB genomic RNA. Amino acid sequence comparisons between the nonstructural ORF of RUB and alphaviruses revealed only one short (122 amino acids) region of significant homology, indicating that these viruses are only distantly related. This region of homology is located at the NH2 terminus of nsP3 in the alphavirus genome. The RUB nonstructural protein ORF contains two global amino acid motifs conserved in a large number of positive-polarity RNA viruses, a motif indicative of helicase activity and a motif indicative of replicase activity. The order of the helicase motif and the nsP3 homology region in the RUB genome is reversed with respect to the alphavirus genome indicating that a genetic rearrangement has occurred during the evolution of these viruses.

Amino Acid Sequence↗
PubMed1999

Compilation and analysis of plant mitochondrial promoter sequences: An illustration of a divergent evolution between monocot and dicot mitochondria.

We have analyzed 67 sequences surrounding transcription initiation sites identified in higher plant mitochondria. The sequences were classified, independently for monocots and dicots, according to the presence of the CRTA core element found upstream of the first transcribed nucleotide and previously reported as an essential element of plant mitochondrial consensus promoters. This compilation provides new elements concerning the structure of consensus promoters and the relative importance of non-conserved promoters in plant mitochondria. It can be emphasized that promoter regions exhibit several differences between monocot and dicot mitochondria, presumably reflecting a divergent evolution: The sequences classified among consensus promoters as well as the distance between the first transcribed nucleotide and the core element are highly conserved in dicots while more plasticity is observed in monocots. It also appears that the proportion of promoters with neither the conserved promoter sequence nor any conserved motif is far greater in dicots than in monocots.

Base Sequence↗
PubMed1994

Mitochondrial DNA sequence variation in human evolution and disease.

Germ-line and somatic mtDNA mutations are hypothesized to act together to shape our history and our health. Germ-line mtDNA mutations, both ancient and recent, have been associated with a variety of degenerative diseases. Mildly to moderately deleterious germ-line mutations, like neutral polymorphisms, have become established in the distant past through genetic drift but now may predispose certain individuals to late-onset degenerative diseases. As an example, a homoplasmic, Caucasian, tRNA(Gln) mutation at nucleotide pair (np) 4336 has been observed in 5% of Alzheimer disease and Parkinson disease patients and may contribute to the multifactorial etiology of these diseases. Moderately to severely deleterious germ-line mutations, on the other hand, appear repeatedly but are eliminated by selection. Hence, all extant mutations of this class are recent and associated with more devastating diseases of young adults and children. Representative of these mutations is a heteroplasmic mutation in MTND6 at np 14459 whose clinical presentations range from adult-onset blindness to pediatric dystonia and basal ganglial degeneration. To the inherited mutations are added somatic mtDNA mutations which accumulate in random arrays within stable tissues. These mutations provide a molecular clock that measures our age and may cause a progressive decline in tissue energy output that could precipitate the onset of degenerative diseases in individuals harboring inherited deleterious mutations.

Amino Acid Sequence↗
PubMed2001

The human olfactory subgenome: from sequence to structure and evolution.

Olfactory receptors (ORs) constitute the largest multigene family in multicellular organisms. Their evolutionary proliferation has been driven by the need to provide recognition capacity for millions of potential odorants with arbitrary chemical configurations. Human genome sequencing has provided a highly informative picture of the "olfactory subgenome", the repertoire of OR genes. We describe here an analysis of 224 human OR genes, a much larger number than hitherto systematically analyzed. These are derived by literature survey, data mining at 14 genomic clusters, and by an OR-targeted experimental sequencing strategy. The presented set contains at least 53% pseudogenes and is minimally divided into 11 gene families. One of these (no. 7) has undergone a particularly extensive expansion in primates. The analysis of this collection leads to insight into the origin of OR genes, suggesting a graded expansion through mammalian evolution. It also allows us to delineate a structural map of the respective proteins. A sequence database and analysis package is provided (http://bioinformatics.weizmann.ac.il/HORDE), which will be useful for analyzing human OR sequences genome-wide.

Amino Acid Sequence↗
PubMed2006

Probing the W chromosome of the codling moth, Cydia pomonella, with sequences from microdissected sex chromatin.

The W chromosome of the codling moth, Cydia pomonella, like that of most Lepidoptera species, is heterochromatic and forms a female-specific sex chromatin body in somatic cells. We collected chromatin samples by laser microdissection from euchromatin and W-chromatin bodies. DNA from the samples was amplified by degenerate oligonucleotide-primed polymerase chain reaction (DOP-PCR) and used to prepare painting probes and start an analysis of the W-chromosome sequence composition. With fluorescence in situ hybridization (FISH), the euchromatin probe labelled all chromosomes, whereas the W-chromatin DNA proved to be a highly specific W-chromosome painting probe. For sequence analysis, DOP-PCR-generated DNA fragments were cloned, sequenced, and tested by Southern hybridization. We recovered single-copy and low-copy W-specific sequences, a sequence that was located only in the W and the Z chromosome, multi-copy sequences that were enriched in the W chromosome but occurred also elsewhere, and ubiquitous multi-copy sequences. Three of the multi-copy sequences were recognized as derived from hitherto unknown retrotransposons. The results show that our approach is feasible and that the W-chromosome composition of C. pomonella is not principally different from that of Bombyx mori or from that of Y chromosomes of several species with an XY sex-determining mechanism. The W chromosome has attracted repetitive sequences during evolution but also contains unique sequences.

Animals↗
PubMed1984

Induction by cAMP of the mRNA encoding the cytosolic form of phosphoenolpyruvate carboxykinase (GTP) from the chicken. Identification and characterization of a cDNA clone for the enzyme.

Previous work from our laboratory (Hod, Y., Utter, M. F., and Hanson, R. W. (1982) J. Biol. Chem. 257, 13787-13794) has demonstrated that chicken kidney contains both mitochondrial and cytosolic forms of phosphoenolpyruvate carboxykinase (GTP) (EC 4.1.1.32) and that the two forms are distinct proteins. Using poly(A+) RNA from chicken kidney, a double-stranded cDNA library was constructed. DNA clones containing sequences complementary to the mRNA for the cytosolic form of phosphoenolpyruvate carboxykinase were initially identified by colony hybridization with 32P-labeled cDNA transcribed from an RNA fraction enriched for the enzyme mRNA. The identity of plasmids containing phosphoenolpyruvate carboxykinase cDNA was confirmed by hybrid-selected translation. Mature mRNA for cytosolic phosphoenolpyruvate carboxykinase of the chicken is 2.8 kilobases in length, similar to that previously noted for mRNA coding for the same enzyme in the rat. The cDNA for the chicken enzyme hybridizes with several restriction fragments of the corresponding cDNA for the rat cytosolic phosphoenolpyruvate carboxykinase, indicating conservation of nucleotide sequences during evolution. Wide spread conservation of sequence homology is also demonstrated by the hybridization of the cDNA for the rat phosphoenolpyruvate carboxykinase with a 2.8-kilobase RNA from the livers of a variety of vertebrates including amphibian, avian, and primate species. Specific mRNA coding for the cytosolic form of phosphoenolpyruvate carboxykinase was present in chicken kidney but absent from the liver, even in animals starved for 48 h. However, the administration of cAMP to normal fed chickens caused a rapid induction of phosphoenolpyruvate carboxykinase mRNA. These findings suggest that the gene for the cytosolic enzyme in chicken liver can be expressed if the proper hormonal stimuli are present.

Animals↗
PubMed2001

Species-specific evolution of repeated DNA sequences in great apes.

DNA sequencing reveals that the genomes of the human, gorilla and chimpanzee share more than 98% homology. Comparative chromosome painting and gene mapping have demonstrated that only a few rearrangements of a putative ancestral mammalian genome occurred during great ape and human evolution. However, interspecies representational difference analysis (RDA) of the gorilla between human and gorilla revealed gorilla-specific DNA sequences. Cloning and sequencing of gorilla-specific DNA sequences indicate that there are repetitive elements. Gorilla-specific DNA sequences were mapped by fluorescence in-situ hybridization (FISH) to the subcentromeric/centromeric regions of three pairs of gorilla submetacentric chromosomes. These sequences could represent either ancient sequences that got lost in other species, such as human and orang-utan, or, more likely, recent sequences which evolved or originated specifically in the gorilla genome.

Animals↗
PubMed2002

Pituitary adenylate cyclase-activating polypeptide and growth hormone-releasing hormone-like peptide in sturgeon, whitefish, grayling, flounder and halibut: cDNA sequence, exon skipping and evolution.

To better understand the evolution of pituitary adenylate cyclase-activating polypeptide (PACAP) and growth hormone-releasing hormone (GHRH), we isolated the cDNAs encoding these peptides from the brains of five species of fish: sturgeon, whitefish, grayling, flounder and halibut. Both hormones are encoded in tandem in full-length cDNAs. We compared the phylogenetic relationship among these and other known sequences encoding PACAP. In closely related species, transcripts encoding PACAP and GHRH are strongly conserved in the hormone coding regions, moderately conserved in the signal peptide, cryptic peptide and 3'-untranslated regions, but are most varied in the 5'-untranslated regions.Next, we compared the deduced amino acid sequences for the peptides to known sequences. Sturgeon and whitefish have a PACAP(38) peptide sequence that is 92% conserved compared to human PACAP(38), the highest for a fish reported to date. GHRH is the lesser conserved of the two peptides with only 39% to 45% conservation between fish and human.Each of the five fish species had a second cDNA encoding a short precursor lacking GHRH(1-32), the bioactive portion of GHRH. This suggests that exon skipping in GHRH-PACAP transcripts may be an important mechanism for regulating the ratio of PACAP to GHRH peptides.

Alternative Splicing↗
PubMed2004

Multi-species sequence comparison reveals dynamic evolution of the elastin gene that has involved purifying selection and lineage-specific insertions/deletions.

BACKGROUND: The elastin gene (ELN) is implicated as a factor in both supravalvular aortic stenosis (SVAS) and Williams Beuren Syndrome (WBS), two diseases involving pronounced complications in mental or physical development. Although the complete spectrum of functional roles of the processed gene product remains to be established, these roles are inferred to be analogous in human and mouse. This view is supported by genomic sequence comparison, in which there are no large-scale differences in the ~1.8 Mb sequence block encompassing the common region deleted in WBS, with the exception of an overall reversed physical orientation between human and mouse. RESULTS: Conserved synteny around ELN does not translate to a high level of conservation in the gene itself. In fact, ELN orthologs in mammals show more sequence divergence than expected for a gene with a critical role in development. The pattern of divergence is non-conventional due to an unusually high ratio of gaps to substitutions. Specifically, multi-sequence alignments of eight mammalian sequences reveal numerous non-aligning regions caused by species-specific insertions and deletions, in spite of the fact that the vast majority of aligning sites appear to be conserved and undergoing purifying selection. CONCLUSIONS: The pattern of lineage-specific, in-frame insertions/deletions in the coding exons of ELN orthologous genes is unusual and has led to unique features of the gene in each lineage. These differences may indicate that the gene has a slightly different functional mechanism in mammalian lineages, or that the corresponding regions are functionally inert. Identified regions that undergo purifying selection reflect a functional importance associated with evolutionary pressure to retain those features.

Animals↗
PubMed1979

Analysis of the constancy of DNA sequences during development and evolution of the nematode Caenorhabditis elegans.

In order to test for the occurrence of rearrangements in DNA during development and to assess the rate of DNA divergence during evolution, we have compared restriction fragments derived from DNA from four sources: sperm cells and somatic tissues of one strain of the nematode Caenorhabditis elegans, somatic tissues of a second strain of the same species, and whole animals of a closely related species. Restriction fragments were detected by hybridizing radioactive cloned fragments to restriction digests that had been fractionated by size on agarose gels and transferred to nitrocellulose sheets. In this way, approximately 50 BamHI restriction fragments were visualized and compared. Fragments from sperm and somatic DNAs were found to be identical; 15% differed in size between the two strains. Little cross homology was found between the two species. We conclude that, if rearrangements occur in C. elegans DNA during development, they must affect fewer than a few percent of the restriction fragments or restriction sites. The difference found between the two strains and the two species is surprisingly great.

Animals↗
PubMed1992

The mechanisms controlling ribosomal protein L1 pre-mRNA splicing are maintained in evolution and rely on conserved intron sequences.

Sequences corresponding to the third intron of the X.laevis L1 ribosomal protein gene were isolated from the second copy of the X.laevis gene and from the single copy of X.tropicalis. Sequence comparison revealed that the three introns share an unusual sequence conservation which spans a region of 110 nucleotides. In addition, they have the same suboptimal 5' splice sites. The three introns show similar features upon oocyte microinjection: they have very low splicing efficiency and undergo the same site specific cleavages which lead to the accumulation of truncated molecules. Computer analysis and RNAse digestions have allowed to assign to the conserved region a specific secondary structure. Mutational analysis has shown that this structure is important for conferring the cleavage phenotype to these three introns. Competition experiments show that the cleavage phenotype can be prevented by coinjection of excess amounts of homologous sequences.

Animals↗
PubMed1996

Gene rearrangements in snake mitochondrial genomes: highly concerted evolution of control-region-like sequences duplicated and inserted into a tRNA gene cluster.

Mitochondrial DNA (mtDNA) regions corresponding to two major tRNA gene clusters were amplified and sequenced for the Japanese pit viper, himehabu. In one of these clusters, which in most vertebrates characterized to date contains three tightly connected genes for tRNA(Ile), and tRNA(Gln), and tRNA(Met), a sequence of approximately 1.3 kb was found to be inserted between the genes for tRNA(Ile) and tRNA(Gln). The insert consists of a control-region-like sequence possessing some conserved sequence blocks, and short flanking sequences which may be folded into tRNA(Pro), tRNA(Phe), and tRNA(Leu) genes. Several other snakes belonging to different families were also found to possess a control-region-like sequence and tRNA(Leu) gene between the tRNA(Ile)and tRNA(Gln) genes. We also sequenced a region surrounded by genes for cytochrome b and 12S rRNA, where the control region and genes for tRNA(Pro) and tRNA(Phe) are normally located in the mtDNAs of most vertebrates. In this region of three examined snakes, a control-region-like sequence exists that is almost completely identical to the one found between the tRNA(Ile) and tRNA(Gln) genes. The mtDNAs of these snakes thus possess two nearly identical control-region-like sequences which are otherwise divergent to a large extent between the species. These results suggest that the duplicate state of the control-region-like sequences has long persisted in snake mtDNAs, possibly since the original insertion of the control-region-like sequence and tRNA(Leu) gene into the tRNA gene cluster, which occurred in the early stage of the divergence of snakes. It is also suggested that the duplicated control-region-like sequences at two distant locations of mtDNA have evolved concertedly by a mechanism such as frequent gene conversion. The secondary structures of the determined tRNA genes point to the operation of simplification pressure on the T psi C arm of snake mitochondrial tRNAs.

Animals↗
PubMed1994

Molecular evolution and population genetics of Greater Caribbean green turtles (Chelonia mydas) as inferred from mitochondrial DNA control region sequences.

The molecular evolution and population genetics of migratory green turtles (Chelonia mydas) in the Greater Caribbean were examined with mitochondrial DNA (mtDNA) control region I sequences. A total of 488 base positions (bp) per individual were aligned for 44 individuals from four nesting populations in Florida, Costa Rica, Aves Island (Venezuela), and Surinam. Twelve sequence polymorphisms were detected, representing ten transitions, one transversion, and one 10-bp repeat. Sequence analyses of within- and between-population diversity revealed a deep divergence between western and eastern Caribbean nesting colonies and an inverse relationship between reproductive female population size and mtDNA diversity. In small populations, genetic admixture was important to maintaining high diversity, whereas larger populations appear to have experienced historical bottlenecks or resulted from founder effects. Mitochondrial DNA sequences of the control region offer an order of magnitude greater resolution than restriction site data for addressing questions about mtDNA variation, both within and between populations of green turtles.

Animals↗
PubMed1994

Recent evolutionary history of American Onchocerca volvulus, based on analysis of a tandemly repeated DNA sequence family.

Polymerase chain reaction (PCR) products were characterized for a repeated sequence family (designated "O-150") of the human filarial parasite Onchocerca volvulus. In phylogenetic inferences, the O-150 sequences clustered into closely related groups, suggesting that concerted evolution maintains sequence homology in this family. Using a novel mathematical model based on a nested application of an analysis of variance, we demonstrated that African rainforest and savannah strain parasite populations are significantly different. In contrast, parasites collected in the New World are indistinguishable from African savannah strains of O. volvulus. This finding supports the hypothesis that onchocerciasis was recently introduced into the New World, possibly as a result of the slave trade.

Americas↗
PubMed1999

Neutral evolution of model proteins: diffusion in sequence space and overdispersion.

We stimulate the evolution of model protein sequences subject to mutations. A mutation is considered neutral if it conserves (1) the structure of the ground state, (2) its thermodynamic stability and (3) its kinetic accessibility. All other mutations are considered lethal and are rejected. We adopt a lattice model, amenable to a reliable solution of the protein folding problem. We prove the existence of extended neutral networks in sequence space-sequences can evolve until their similarity with the starting point is almost the same as for random sequences. Furthermore, we find that the rate of neutral mutations has a broad distribution in sequence space. Due to this fact, the substitution process is overdispersed (the ratio between variance and mean is larger than 1). This result is in contrast with the simplest model of neutral evolution, which assumes a Poisson process for substitutions, and in qualitative agreement with the biological data.

Animals↗
PubMed2006

Higher phylogeny of zygaenid moths (Insecta: Lepidoptera) inferred from nuclear and mitochondrial sequence data and the evolution of larval cuticular cavities for chemical defence.

Zygaenid moths are capable of releasing hydrogen cyanide in their defense by enzymatic break-down of cyanoglucosides, but only larvae of chalcosiine and zygaenine moths store cyanogenic compounds in cuticular cavities and thus are able to discharge defense droplets, which effectively deter potential predators. A previously proposed phylogeny of Zygaenidae hypothesized a sister group relationship of chalcosiine and zygaenine moths because of their similar larval defense system. Not all chalcosiine taxa possess cuticular cavities, however, and a comparable defense mechanism has been reported in larvae of the zygaenoid family Heterogynidae. Considering sequence data of seven molecular loci, the present study estimates the posterior probability of phylogenetic hypotheses explaining the occurrence of larval cuticular cavities. The molecular data confirm the previous exclusion of Himantopteridae from Zygaenidae and suggest their close affinity to Somabrachyidae. The sequence data also corroborate the recently proposed exclusion of the Phaudinae from the Zygaenidae, because this subfamily is recovered in a reasonably well supported species cluster consisting of members of the families Lacturidae, Limacodidae, Himantopteridae, and Somabrachyidae. We consequently agree to raise Phaudinae to family rank. Within Zygaenidae, the subfamilies Callizygaeninae, Chalcosiinae, and Procridinae most likely constitute a monophyletic group, which is sister to the Zygaeninae. Our results imply that cuticular cavities were probably present in the larvae of the most recent common ancestor of Zygaenidae. Heterogynidae cannot be confirmed as sister taxon to this family, but appear at the very first split of the Zygaenoidea, although with poor support. The specific pattern of taxa in the molecular phylogeny showing larval cuticular cavities opens the possibility that these structures could have been already present in the most recent common ancestor of the Zygaenoidea.

Animals↗
PubMed2004

Sequence composition, organization, and evolution of the core Triticeae genome.

We investigated the composition and the basis of genome expansion in the core Triticeae genome using Aegilops tauschii, the D-genome donor of bread wheat. We sequenced an unfiltered genomic shotgun (trs) and a methylation-filtration (tmf) library of A. tauschii, and analyzed wheat expressed sequence tags (ESTs) to estimate the expression of genes and transposable elements (TEs). The sampled D-genome sequences consisted of 91.6% repetitive elements, 2.5% known genes, and 5.9% low-copy sequences of unknown function. TEs constituted 68.2% of the D-genome compared with 50% in maize and 14% in rice. The DNA transposons constituted 13% of the D-genome compared with 2% in maize. TEs were methylated unevenly within and among elements and families, and most were transcribed which contributed to genome expansion in the core Triticeae genome. The copy number of a majority of repeat families increased gradually following polyploidization. Certain TE families occupied discrete chromosome territories. Nested insertions and illegitimate recombination occurred extensively between the TE families, and a majority of the TEs contained internal deletions. The GC content varied significantly among the three sequence sets examined ranging from 42% in tmf to 46% in trs and 52% in the EST. Based on enrichment of genic sequences, methylation-filtration offers one option, although not as efficient as in maize, for isolating gene-rich regions from the large genome of wheat.

Edible Grain↗