Telomere Maintenance in Organisms without Telomerase

Mason, James; Reddy, Hemakumar M.; Frydrychová, Radmila Čapková

doi:10.5772/19348

Cited by 5 publications

(4 citation statements)

References 114 publications

(133 reference statements)

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“…Some organisms have lost the telomeric DNA repeats maintained by telomerase and have replaced them with tandem arrangements of satellite DNA sequences that can be extended by copying information from one chromosome to another [52]. Homologous recombination of long satellite sequences at telomeres has been described in representatives of lower Diptera [52]. Our results may suggest that an unknown telomere repeat motif of Acanthocephala species may be associated with GC bases.…”

Section: Standard Chromosome Complementmentioning

confidence: 61%

“…The composition of telomeric repeats in Acanthocephala species is still unknown, and it remains unclear whether there is a novel telomeric motif or another mechanism that replaces telomerase in maintaining telomere length. Some organisms have lost the telomeric DNA repeats maintained by telomerase and have replaced them with tandem arrangements of satellite DNA sequences that can be extended by copying information from one chromosome to another [52]. Homologous recombination of long satellite sequences at telomeres has been described in representatives of lower Diptera [52].…”

Section: Standard Chromosome Complementmentioning

confidence: 99%

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Karyological Study of Acanthocephalus lucii (Echinorhynchida): The Occurrence of B Chromosomes in Populations from PCB-Polluted Waters

Marková,

Orosová,

Marec

et al. 2024

Diversity

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In this study, we performed a cytogenetic analysis of Acanthocephalus lucii specimens from three sites with different levels of environmental pollution. Standard and fluorochrome staining (CMA3/DAPI), fluorescence in situ hybridization (FISH) with 18S rDNA and histone H3 probes, and silver impregnation were performed. Chromosome complements of 2n = 7/8 (male/female), n = 1m + 2sm + 1a (X), and CMA3-positive bands in all chromosomes were found in all three populations. FISH revealed one 18S rDNA locus on the X chromosome and one locus of H3 histone genes on the first chromosome pair. At the intraspecific level, the populations differed in the presence of supernumerary B chromosomes, which were found in all specimens from Zemplínska Šírava and in 89.4% of specimens from the Laborec River, but not at the reference site. The first two sites are considered to be water bodies with high toxin contamination. Based on this fact, we assume an increased frequency of chromosome breaks leading to the formation of DNA fragments that have the potential to form B chromosomes. The present results add to the very limited data on the organization of multigene families in the genome of Acanthocephala and suggest a possible causal link between water pollution and the occurrence of B chromosomes in fish parasites.

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Section: Standard Chromosome Complementmentioning

confidence: 61%

Section: Standard Chromosome Complementmentioning

confidence: 99%

Karyological Study of Acanthocephalus lucii (Echinorhynchida): The Occurrence of B Chromosomes in Populations from PCB-Polluted Waters

Marková,

Orosová,

Marec

et al. 2024

Diversity

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show abstract

“…Unexpectedly, we also observed a striking upregulation of certain non-coding RNAs, particularly retrotransposable elements. Among these, HeT-A, TART, and TAHRE are of particular interest due to their unique characteristics as telomeric retrotransposons (TRs), which play an essential role in the maintenance of telomere length in insects (Frydrychova et al, 2008;Mason et al, 2008;Mason, 2011;Pardue and DeBaryshe, 2011). We verified that these TRs were upregulated in both Cdk8 and CycC mutants using qRT-PCR with the non-LTR retrotransposon jockey (jockey gag) and non-retrotransposon RNA Pol II-transcribed RasGAP gene as controls (Fig.…”

Section: Elevated Telomeric-specific Retrotransposon Expression and I...mentioning

confidence: 76%

Transcriptional coupling of telomeric retrotransposons with the cell cycle

Liu,

Xie,

et al. 2023

Preprint

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Instead of employing telomerases to safeguard chromosome ends, dipteran species maintain their telomeres by transposition of telomeric-specific retrotransposons (TRs): inDrosophila, these areHeT-A,TART, andTAHRE. Previous studies have shown how these TRs create tandem repeats at chromosome ends, but the exact mechanism controlling TR transcription has remained unclear. Here we report the identification of multiple subunits of the transcription cofactor Mediator complex and transcriptional factors Scalloped (Sd, the TEAD homolog in flies) and E2F1-Dp as novel regulators of TR transcription and telomere length inDrosophila. Depletion of multiple Mediator subunits, Dp, or Sd increased TR expression and telomere length, while over-expressing E2F1-Dp or knocking down the E2F1 regulator Rbf1 (Retinoblastoma-family protein 1) stimulated TR transcription, with Mediator and Sd affecting TR expression through E2F1-Dp. The CUT&RUN analysis revealed direct binding of CDK8, Dp, and Sd to telomeric repeats. These findings highlight the essential role of the Mediator complex in maintaining telomere homeostasis by regulating TR transcription through E2F1-Dp and Sd, revealing the intricate coupling of TR transcription with the host cell-cycle machinery, thereby ensuring chromosome end protection and genomic stability during cell division.

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“…Additionally, we were also not able to identify a homolog of C. elegans telomerase ( trt-1; ACC: NM_001373211.4) in our assembly. This may suggest that non-standard telomere processes might be operating in root-knot nematodes as has been found for fruit flies [49,50] .…”

Section: Discussionmentioning

confidence: 95%

Phased chromosome-scale genome assembly of an asexual, allopolyploid root-knot nematode reveals complex subgenomic structure

Winter

Taranto

Yimer

et al. 2023

Preprint

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We present the chromosome-scale genome of the allopolyploid root-knot nematode Meloidogyne javanica. We show that the M. javanica genome is predominantly allotetraploid, comprising two subgenomes, A and B, that most likely originated from hybridisation of two ancestral parental species. The assembly is annotated using full-length non-chimeric transcripts, comparison to reference databases, and ab initio prediction techniques, and the subgenomes are phased using ancestral k-mer spectral analysis. Subgenome B appears to show greater fission of chromosomal contigs, and while there is substantial synteny between subgenomes, we also identify regions lacking synteny that may have diverged in the ancestral genomes prior to or following hybridisation. Indels are common both between alleles within a subgenome, and between the A and B subgenomes, suggesting the M. javanica genome exists in a dynamic hypo-tetraploidy where copy number can vary along the chromosome. This annotated and phased genome assembly forms a significant resource for understanding the origins and genetics of these globally important plant pathogens.

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Telomere Maintenance in Organisms without Telomerase

Cited by 5 publications

References 114 publications

Karyological Study of Acanthocephalus lucii (Echinorhynchida): The Occurrence of B Chromosomes in Populations from PCB-Polluted Waters

Karyological Study of Acanthocephalus lucii (Echinorhynchida): The Occurrence of B Chromosomes in Populations from PCB-Polluted Waters

Transcriptional coupling of telomeric retrotransposons with the cell cycle

Phased chromosome-scale genome assembly of an asexual, allopolyploid root-knot nematode reveals complex subgenomic structure

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