Repeated Genes in Eukaryotes

Long, Eric O.; Dawid, Igor B.

doi:10.1146/annurev.bi.49.070180.003455

Cited by 1,307 publications

(676 citation statements)

References 2 publications

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“…Since the latter approach measured the expression of only the single-copy DNA sequences, while the [3 H]cDNA method includes analysis of all DNA sequences classes, it is apparent that the repetitive DNA sequences are quite likely represented in the mRNA population. This is not surprising in view of previous observations with other organisms [22]. Second, it is also clear that about 50% of the total mass of the mRNA is occupied by only 700-800 different mRNA species, or about 5% of the total mRNA [aH]cDNA was reacted with excess poly(A)÷-mRNA (A) as described in Materials and Methods.…”

Section: Polysomal Poly(a)*-mrna-[3h]cdna Hybridization the Experimementioning

confidence: 52%

“…Such mRNAs would contribute to the total poly(A)÷-mRNA complexity as measured by the [3H]cDNA approach, but would be refractory to analysis by hybridization of poly(A)÷-mRNA to 3H-labeled single-copy DNA sequences. Since mRNAs complementary to repetitive DNA sequences have been observed in numerous eukaryotic systems [22], we believe this is also the case in T. cruzi. It must, however, also be recognized that even the best theoretical description of a complex reassociation profile contains the inherent difficulty that a significant range in sequence complexity can be obtained within a two-fold range in the root mean square (RMS) of the computer solution to the data.…”

Section: Discussionmentioning

confidence: 69%

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Complexity and content of the DNA and RNA in Trypanosoma cruzi

Lanar

Lévy

Manning

1981

Molecular and Biochemical Parasitology

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The content and sequence complexity of the nuclear DNA and messenger RNA for epimastigotes of Trypanosoma cruzi were determined. From analysis of nuclear DNA reassociation studies and microspectrofluorometric measurements of laser induced fluorescence of cellular DNA, T. cruzi is found to be a diploid organism with a nuclear DNA content of 2.5 x 108 nucleotide pairs (2.8 X 10 -~3 g) and a kinetoplast DNA content of 4.9 X 107 nucleotide pairs (5.4 X 10 -t4 g). Reassoeiation kinetics of nuclear DNA of average length 0.4 kb reveals three kinetic components: a moderately repetitive component with a reiteration frequency of 5.1 X 103 present in 9% of the fragments, a lowly repetitive component with a reiteration frequency of 32 present in 51% of the fragments, and a single-copy component present in 23% of the fragments.By saturation hybridization of total polysomal RNA to 3H-labeled single-copy DNA, it was determined that 68% of the single-copy DNA was represented in the epimastigote polysomal RNA. This corresponds to ca. 12 000 different mRNA species. Of these, ca. 9000 are present as poly(A)÷-RNA, while the remaining 3000 appear not to be polyadenylated. Kinetic analysis of the poly(A)+-RNA population indicates it is composed of at least three classes of RNAs of different abundancy levels: two sequences which occur ca. 3000 times per cell, ca. 750 sequences which occur about 20 times per cell, and ca. 15 500 sequences which occur 1-2 times per cell.

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Section: Polysomal Poly(a)*-mrna-[3h]cdna Hybridization the Experimementioning

confidence: 52%

Section: Discussionmentioning

confidence: 69%

Complexity and content of the DNA and RNA in Trypanosoma cruzi

Lanar

Lévy

Manning

1981

Molecular and Biochemical Parasitology

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“…However, the spacer sequences between the coding regions of the ribosomal cistron tend to diverge rapidly (Long & Dawid, 1980), which probably accounts for the distinctive, species-characteristic restriction fragments shown above. The most useful enzymes for demonstrating this are Taq I and Mbo I; the latter distinguishes between B. malayi and B. pahangi as well as all the other nematodes tested.…”

Section: Discussionmentioning

confidence: 99%

Use of restriction fragment length polymorphisms (RFLPs) to distinguish between nematodes of pathogenic significance

et al. 1988

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SUMMARYThe availability of restriction fragment length polymorphisms (RFLPs) would be useful for studying the extent of diversity among morpholgically indistinguishable populations of filarial parasites. Such polymorphisms may be useful in correlating various physiological and clinical differences with parasite heterogeneity. In order to identify such RFLPs, we isolated DNA from microfilaria of 6 filarial species (Acanthocheilonema viteae, Brugia malayi, Brugia pahangi, Dirofilaria immitis, Litomosoides carinii and Setaria digitatum), digested the DNA with several restriction endonucleases, prepared Southern blots and probed with 32 P-labelled DSA probes. The patterns of fragments generated using two restriction endonucleases, Mbo I and Taq I, in combination with two probes, rDNA from the free-living soil nematode Caenorhabditis elegans, and pBM103, an anonymous DNA probe from B. malayi, unequivocally distinguish between all 6 of the species. To ensure that the differences we observed between the species represent true interspecies variation rather than fortuitous individual variations we analysed DNA from several individual B. malayi and B. pahangi worms. The individual B. malayi worms demonstrated restriction profiles that were invariant, as did the individual B. pahangi worms, demonstrating that the differences we observed were true interspecies variations.

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“…Ribosomal RNA genes are typically organized in the eukaryotic genomes as tandem repeats comprising SSU rRNA gene, a cluster of internal transcribed spacers and 5.8S rRNA gene (ITS1-5.8S-ITS2), and LSU rRNA gene (reviewed in e.g., Long and Dawid 1980). Multiple copies of this array are usually present in the genome, but in most organisms they show little to no intragenomic variability due to the process of concerted evolution, which homogenizes sequences of multiple-copy genes within a genome (e.g., Brown et al 1972;Dover 1982;Elder and Turner 1995;Ganley and Kobayashi 2007;Liao 1999).…”

Section: Unusual Pattern Of Ssu Rrna Gene Variability In Ripellamentioning

confidence: 99%

Two new species of Ripella (Amoebozoa, Vannellida) and unusual intragenomic variability in the SSU rRNA gene of this genus

Kudryavtsev

Гладких

2017

European Journal of Protistology

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Two new species, Ripella decalvata and R. tribonemae (Amoebozoa, Vannellida), are described and the diversity of known strains assigned to the genus analyzed. Ripella spp. are closely similar to each other in the light microscopic characters and sequences of small-subunit (SSU) ribosomal RNA gene, but differences in the cell coat structure and cytochrome oxidase (COI) gene sequences are more prominent. SSU rRNA in R. platypodia CCAP1589/2, R. decalvata and R. tribonemae demonstrates an unusual pattern of intragenomic variation. Sequencing of multiple molecular clones of this gene produced numerous sequence variants in a number of specific sites. These sites were usually terminal parts of several variable helices in all studied strains. Analysis of all known Ripella strains shows that SSU rRNA sites differing between strains of different origin are mainly restricted to these areas of the gene. There are only two sites, which differ between strains, but not within genomes. This intragenomic variability of the SSU rRNA gene, seemingly characteristic of all Ripella spp., was never reported to be so extensive in Amoebozoa. The data obtained show another example of complex organization of rRNA gene cluster in protists and emphasize caution needed when interpreting the metagenomic data based on this marker.

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Repeated Genes in Eukaryotes

Cited by 1,307 publications

References 2 publications

Complexity and content of the DNA and RNA in Trypanosoma cruzi

Complexity and content of the DNA and RNA in Trypanosoma cruzi

Use of restriction fragment length polymorphisms (RFLPs) to distinguish between nematodes of pathogenic significance

Two new species of Ripella (Amoebozoa, Vannellida) and unusual intragenomic variability in the SSU rRNA gene of this genus

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