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PubMed1996

Genomic repetitive DNA elements of Trypanosoma cruzi.

Repetitive DNA sequences are interspersed throughout the genomes of mammals and other higher eukaryotes, and represent a substantial portion of the genome. Although it has been generally assumed that the redundant DNA is present only in the complex genomes of high order organisms, over the past few years a number of repetitive DNA sequences have been also detected in the protozoan parasite Trypanosoma cruzi. A compilation of the repetitive DNA sequences found in the T. cruzi genome is here presented by Jose Maria Requena, Manuel Carlos López and Carlos Alonso, who also speculate on their possible origin and functional implications regarding retrotransposition and gene regulation.

Journal Article↗
PubMed1998

Sequence heterogeneity in a repetitive DNA element of Fasciola.

A repetitive DNA sequence used as a specific probe for Fasciola hepatica infections in snails was examined in F. hepatica and Fasciola gigantica (36 individuals) specimens from five continents. The degree of intraspecific identity ranged from 79 to 99% in F. hepatica and from 93 to 99% in F. gigantica. The interspecific identity ranged from 81 to 100%, confirming the suggestion that the DNA probe sequence could be used worldwide as an epidemiological tool for the examination of the intermediate host snail in fasciolosis. Differentiation between F. hepatica and F. gigantica infections in snails was not possible using the probe.

Animals↗
PubMed1985

Rat LINE1: the origin and evolution of a family of long interspersed middle repetitive DNA elements.

We present approximately 7.0 kb of composite DNA sequence of a long interspersed middle repetitive element (LINE1) present in high copy number in the rat genome. The family of these repeats, which includes transcribing members, is the rat homologue of the mouse MIF-Bam-R and human Kpn I LINEs. Sequence alignments between specimens from these three species define the length of a putative unidentified open reading frame, and document extensive recombination events that, in conjunction with retroposition, have generated this large family of pseudogenes and pseudogene fragments. Comparative mapping of truncated elements indicates that a specific endonucleolytic activity might be involved in illegitimate (nonhomologous) recombination events. Sequence divergence analyses provide insights into the origin and molecular evolution of these elements.

Amino Acid Sequence↗
PubMed1983

Association of two different repetitive DNA elements near immunoglobulin light chain genes.

Sequence studies of repetitive DNA elements approximately 6 kb 3' of the mouse immunoglobulin CK region gene show that the R element located there (Gebhard et al. (1982) J. Mol. Biol. 157, 453-471) is adjacent to a 500 base pair long element which shows 80% homology to the BAM5 element sequenced by Fanning (Nuc. Acids Res. (1982), 10, 5003-5013). Neither the BAM5 element nor the R element itself is surrounded by a direct repeat, but the composite element (BAM5 + R) is surrounded by a 15 base pair direct repeat (with one mismatch). Direct repeats, consisting of target site sequences that surround a repetitive DNA element, are thought to arise during the insertion of the element at that site. It therefore appears that the BAM5 and R elements interacted and inserted as a linked entity. The existence of other BAM5/R composites throughout the mouse lambda chain locus indicates that BAM5-R cooperation is not a rare event.

Animals↗
PubMed1996

A conserved repetitive DNA element located in the centromeres of cereal chromosomes.

Repetitive DNA sequences have been demonstrated to play an important role for centromere function of eukaryotic chromosomes, including those from fission yeast, Drosophila melanogaster, and humans. Here we report on the isolation of a repetitive DNA element located in the centromeric regions of cereal chromosomes. A 745-bp repetitive DNA clone pSau3A9, was isolated from sorghum (Sorghum bicolor). This DNA element is located in the centromeric regions of all sorghum chromosomes, as demonstrated by fluorescence in situ hybridization. Repetitive DNA sequences homologous to pSau3A9 also are present in the centromeric regions of chromosomes from other cereal species, including rice, maize, wheat, barley, rye, and oats. Probe pSau3A9 also hybridized to the centromeric region of B chromosomes from rye and maize. The repetitive nature and its conservation in distantly related plant species indicate that the pSau3A9 family may be associated with centromere function of cereal chromosomes. The absence of DNA sequences homologous to pSau3A9 in dicot species suggests a faster divergence of centromererelated sequences compared with the telomere-related sequences in plants.

Animals↗
PubMed1997

Beta, a novel repetitive DNA element associated with tRNA genes in the pathogenic yeast Candida albicans.

We have identified a novel 399 bp repetitive DNA element (which we designate beta) 9bp upstream of a seryl-tRNA(CAG) gene in the genome of Candida albicans. There are two copies of the seryl-tRNA(CAG) gene, one on each homologue of chromosome VI, and the beta element is found upstream of one copy of the gene in C. albicans strain 2005E. The beta element is not present upstream of either copy of the seryl-tRNA(CAG) gene in eight other laboratory strains of C. albicans tested, but was detected in this location in several fresh clinical isolates. Southern blot analysis indicated that there are approximately eight copies of the beta element per diploid C. albicans genome and that it is a mobile element, being present on at least two different chromosomes. Three unique genomic DNA clones containing the beta element were isolated from strain 2005E; in each case, a different tRNA gene was found immediately adjacent to the beta element. Three new tRNA genes from C. albicans have thus been identified: tRNA(Asp), tRNA(Ala) and tRNA(Ile). The beta element shows no significant sequence homology to other known prokaryotic or eukaryotic repetitive elements, although an 8 bp repeat at the 3' end of the element is identical to that of the Ty3 retrotransposable element of Saccharomyces cerevisiae. We propose that the beta element is a solo long terminal repeat (LTR) sequence of a Ty3/gypsy-like transposable element in C. albicans that is closely associated with tRNA genes.

Base Sequence↗
PubMed1993

Repetitive sequences in the ribosomal intergenic spacer of Trypanosoma cruzi.

A fragment of Trypanosoma cruzi ribosomal intergenic spacer (IGS) located at 6.7 kb from the 3' end of the 24S rRNA gene was analyzed. This IGS fragment is characterized by the presence of three types of repetitive elements (designated Spacer Repetitive Elements, SRE), short direct repeats (5-6 bp) and chi-like recombinational sequences. SRE elements are composed of relatively short repeats (43-145 bp) which show variabilities consisting of nucleotide changes, insertions and deletions. SRE-1 element (145 bp) has a short oligo(dA) tail at the end of the repeat and can be found flanked by other SRE elements. SRE elements are species-specific, suggesting that probes based on them may be diagnostic for Trypanosoma cruzi.

Animals↗
PubMed1985

Analysis of repetitive sequence elements containing tRNA-like sequences.

Several repetitive sequence elements from diverse species share extensive sequence homology with tRNA molecules. Analysis of the tRNA-like sequences within these elements suggest that they have originated from authentic tRNA sequences. Elements containing tRNA-like sequences can be divided into three distinct groups whose members share extensive sequence homology, have similar sequence organization and have unique species distribution. We suggest that these three groups represent independent examples of retroposon families that have originated from tRNAs.

Animals↗
PubMed2003

Enrichment for histone H3 lysine 9 methylation at Alu repeats in human cells.

The aim of this study was to identify in human cells common targets of histone H3 lysine 9 (H3-Lys9) methylation, a modification that is generally associated with gene silencing. After chromatin immunoprecipitation using an H3-Lys9 methylated antibody, we cloned the recovered DNA and sequenced 47 independent clones. Of these, 38 clones (81%) contained repetitive elements, either short interspersed transposable element (SINE or Alu elements), long terminal repeat (LTR), long interspersed transposable element (LINE), or satellite region (ALR/Alpha) DNA, and three additional clones were near Alu elements. Further characterization of these repetitive elements revealed that 32 clones (68%) were Alu repeats, corresponding to both old Alu (23 clones) and young Alu (9 clones) subfamilies. Association of H3-Lys9 methylation was confirmed by chromatin immunoprecipitation-PCR using conserved Alu primers. In addition, we randomly selected 5 Alu repeats from the recovered clones and confirmed association with H3-Lys9 by PCR using primer sets flanking the Alu elements. Treatment with the DNA methyltransferase inhibitor 5-aza-2'-deoxycytidine rapidly decreased the level of H3-Lys9 methylation in the Alu elements, suggesting that H3-Lys9 methylation may be related to the suppression of Alu elements through DNA methylation. Thus H3-Lys9 methylation is enriched at human repetitive elements, particularly Alu elements, and may play a role in the suppression of recombination by these elements.

Alu Elements↗
PubMed2003

Methylation dynamics of repetitive DNA elements in the mouse germ cell lineage.

Repetitive DNA elements account for a substantial fraction of the mammalian genome. Many are subject to DNA methylation, which is known to undergo dynamic change during mouse germ cell development. We found that repeat sequences of three different classes retain high levels of methylation at E12.5, when methylation is erased from many single-copy genes. Maximal demethylation of repeats was seen later in development and at different times in male and female germ cells. At none of the time points examined (E12.5, E15.5, and E17.5) did we see complete demethylation, suggesting that methylation patterns on repeats may be passed on from one generation to the next. In male germ cells, we observed a de novo methylation event resulting in complete methylation of all the repeats in the interval between E15.5 and E17.5, which was not seen in females. These results suggest that repeat sequences undergo coordinate changes in methylation during germ cell development and give further insights into germ cell reprogramming in mice.

Animals↗
PubMed1998

ROn-1 SINEs: a tRNA-derived, short interspersed repetitive DNA element from Oreochromis niloticus and its species-specific distribution in Old World cichlid fishes.

A SINE-like repetitive element (ROn-1) has been cloned from the tilapiine cichlid fish Oreochromis niloticus. The element is 345 base pairs (bp) in length and consists of a transfer-RNA-like domain with putative RNA polymerase III recognition sequences, a tRNA-unrelated region, and a poly(A) tail. Approximately 6000 copies of ROn-1 occur in the haploid genome of O. niloticus. Southern blot analysis revealed that ROn-1 is an abundant element in the genomes of many African cichlid fishes, but absent from the genome of the Indian cichlid Etroplus.

Africa↗
PubMed1992

A temperature-regulated, retrotransposon-like element from Candida albicans.

A repetitive element was isolated from the genome of Candida albicans. This repetitive element, which we designated alpha, was localized to a 500-bp fragment of genomic DNA. The alpha element was dispersed in the genome and varied in copy number and genomic location in the strains examined. Analyses of various loci containing the alpha element identified a locus containing a composite element. This composite element consisted of two direct repeats of the alpha element separated by approximately 5.5 kb of DNA, a structural arrangement similar to that of retrovirus-like transposable elements. The flanking alpha elements of the composite structure were 388 bp in length and were identical in sequence. They were bounded by the nucleotides 5'-TG. ... CA-3', which were part of a delimiting inverted repeat, a feature conserved in the long terminal repeats of retroviruses and retrovirus-like elements. As in retrovirus-like elements, the entire composite element, including the alpha elements, was transcribed into an approximately unit-length mRNA. The expression of this transcript was greatly increased when cells were grown at 25 versus 37 degrees C. As has been found in many retrotransposons, the composite element was flanked by a 5-bp duplication and varied in both copy number and genomic location in various strains. We conclude that the composite element is a retrotransposon-like element, and we have designated this element Tca1. We suggest that Tca1 may be relevant to the genomic evolution of C. albicans and the pathogenic potential of the organism.

Base Sequence↗
PubMed2001

[DRE-PCR (Double Repetitive Element-Polymerase Chain Reaction)--a new molecular-epidemiologic method in the detection of tuberculosis].

In a pilot study Double Repetitive Element-Polymerase Chain Reaction 20 clinical isolates of Mycobacterium tuberculosis from Guatemala and 49 strains from Prague were typed. This technique is based on direct evidence of repetitive elements IS6110 or PGRS and does not require DNA purification, digestion by endonuclease nor Southern blot hybridization. Preliminary examination of Guatemalian strains revealed a striking identity or similarity of DRE-PCR profiles while the Prague strains were characterized by conspicuous polymorphism. The Prague strains were examined in a total number of 13 series of electrophoreograms and subsequently subjected to automated analysis with GelCompar software. The DRE-PCR method is suitable for screening of a major number of clinical isolates of M. tuberculosis in laboratories equipped with a minimum of technical facilities for the PCR method, furthermore it requires facilities for synthesis of the necessary primers and at least basic knowledge of molecular biology.

Bacterial Typing Techniques↗
PubMed1993

SIRE-1, a long interspersed repetitive DNA element from soybean with weak sequence similarity to retrotransposons: initial characterization and partial sequence.

Gm776 is a 776-bp subregion of a member of an interspersed family of relatively homogeneous repetitive DNA elements from soybean (Glycine max). The fragment was originally amplified from soybean DNA by the polymerase chain reaction using a single 22-nucleotide primer, and consequently terminates in an inverted repeat. The elements defined by Gm776 are at least 10.6 kb in length and constitute a family of 500-800 members per haploid genome. The family has been designated SIRE-1 (soybean interspersed repetitive element 1). Overlapping regions of Gm776 exhibit suggestive DNA sequence similarity to Ta1 and Ty1, copia-like retrotransposons from Arabidopsis thaliana and Saccharomyces cerevisiae, respectively. However, there are no similarities at the amino acid level, and the regions of similarity are not functionally related.

Base Sequence↗
PubMed1986

Localization and comparative nucleotide sequence analysis of the transforming domain in herpes simplex virus DNA containing repetitive genetic elements.

The 7.5-kilobase BamHI E fragment (BamHI-E) of herpes simplex virus type 2 (HSV-2) DNA (map position 0.533-0.583) encodes the 144-kDa subunit of ribonucleotide reductase and induces the neoplastic transformation of immortalized cell lines. To define the minimal transforming region of BamHI-E, a series of subclones were constructed that spanned the entire fragment. These subclones were assayed for focus formation in Rat-2 cells. Removal of the promoter region from the viral 144-kDa-protein gene left the transforming activity of DNA clones intact. A 481-bp Pst I-Sal I subclone of BamHI-E was capable of inducing focus formation and tumorigenic conversion. The nucleotide sequence of this fragment and the colinear nontransforming region of HSV-1 DNA was determined and compared. Striking differences were detected in the structure and organization of repeated sequence elements. Specifically, transforming HSV-2 DNA contains multiple regions of alternating purines and pyrimidines, G + C-rich sequences that are potential binding sites for transcription factor Sp1, and insertion-like sequence elements that are interrupted by base substitutions in nontransforming HSV-1 DNA. These results define a distinct transforming domain in HSV-2 DNA composed of repetitive elements implicated in gene rearrangement and activation.

Base Sequence↗
PubMed1987

Cotransposition of a highly repetitive DNA element with flanking sequences in the genome of the midge Chironomus thummi.

A family of highly repetitive DNA elements, the Cla-elements, is present in the genomes of the two sibling species Chironomus th. thummi and Ch. th. piger. These Cla-elements are organized in large tandem repetitive clusters as well as occurring as interspersed monomeric elements, in both subspecies. The analysis of a monomeric Cla-element and several kilobases of its flanking sequences from Ch. th. piger revealed that the short Cla-elements are cotransposed together with adjacent DNA. We found the same association of Cla-elements with specific flanking DNA in clones obtained from the rDNA of Ch. th. thummi and from nonribosomal Cla-DNA of Ch. th. piger. The Cla-element-flanking DNA is clearly also repetitive, but mainly of interspersed organization.

Animals↗
PubMed2004

Mitochondrial DNA-like sequences in the nucleus (NUMTs): insights into our African origins and the mechanism of foreign DNA integration.

Nuclear mitochondrial DNA sequences (NUMTs) are common in eukaryotes. However, the mechanism by which they integrate into the nuclear genome remains a riddle. We analyzed 247 NUMTs in the human nuclear DNA (nDNA), along with their flanking regions. This analysis revealed that some NUMTs have accumulated many changes, and thus have resided in the nucleus a long time, while others are >94% similar to the reference human mitochondrial DNA (mtDNA), and thus must be recent. Among the latter, two NUMTs, encompassing the COI gene, carry a set of transitions characteristic of the extant African-specific L macrohaplogroup mtDNAs and are more homologous to human mtDNA than to chimp. Screening for one of these NUMTs revealed its presence in all human samples tested, confirming that the African macrohaplogroup L mtDNAs were present in the earliest modern humans and thus were the first human mtDNAs. An analysis of flanking sequences of the NUMTs revealed that 59% were within 150 bp of repetitive elements, with 26% being within 15 bp of and 33% being within 15-150 bp of repetitive elements. Only 14% were integrated into a repetitive element. This association of NUMTs with repetitive elements is highly nonrandom (p<0.001). These data suggest that the vicinity of transposable elements influences the ongoing integration of mtDNA sequences and their subsequent duplication within the nDNA. Finally, NUMTs appear to preferentially integrate into DNA with different GC content than the surrounding chromosomal band. Our results suggest that chromosomal structure might influence integration of NUMTs.

Africa↗
PubMed1998

Effects of Alu insertions on gene function.

Alu elements are a family of short interspersed repetitive elements (SINEs) found exclusively in primates. These elements are around 300 base pairs long, are found in excess of one million copies per diploid genome, and are dispersed throughout the human genome. Alu elements are scattered by a mechanism called "retrotransposition". Three independent steps are involved in retrotransposition: transcription of the Alu repetitive element, reverse transcription of the Alu RNA and integration of the Alu cDNA. The fact that Alu elements retrotranspose so readily suggests that they have a myriad of effects on the genome, mostly by inactivating genes or altering their function. These characteristics of Alu repetitive elements point to these repetitive DNA fragments as a major driving force for evolution. In addition, Alu elements are known to adopt diverse functions depending on the context of the surrounding genetic material into which they insert. In this article, we review some of the evidence that demonstrates the functional significance of Alu repeats.

Alu Elements↗