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The heterochromatic chromosome caps in great apes impact telomere metabolism.

Novo C, Arnoult N, Bordes WY, Castro-Vega L, Gibaud A, Dutrillaux B, Bacchetti S, Londoño-Vallejo A - Nucleic Acids Res. (2013)

Bottom Line: In contrast with the limited sequence divergence accumulated after separation of higher primate lineages, marked cytogenetic variation has been associated with the genome evolution in these species.Studying the impact of such structural variations on defined molecular processes can provide valuable insights on how genome structural organization contributes to organismal evolution.In gorilla, on the other hand, a proportion of the subtelomeric heterochromatic caps present in most chromosome arms are associated with large blocks of telomere-like sequences that follow a replication program different from that of bona fide telomeres.

View Article: PubMed Central - PubMed

Affiliation: Telomeres and Cancer laboratory, 'Equipe Labellisée Ligue contre le Cancer', UMR3244, Institut Curie, 26 rue d'Ulm, 75248 Paris, France.

ABSTRACT
In contrast with the limited sequence divergence accumulated after separation of higher primate lineages, marked cytogenetic variation has been associated with the genome evolution in these species. Studying the impact of such structural variations on defined molecular processes can provide valuable insights on how genome structural organization contributes to organismal evolution. Here, we show that telomeres on chromosome arms carrying subtelomeric heterochromatic caps in the chimpanzee, which are completely absent in humans, replicate later than telomeres on chromosome arms without caps. In gorilla, on the other hand, a proportion of the subtelomeric heterochromatic caps present in most chromosome arms are associated with large blocks of telomere-like sequences that follow a replication program different from that of bona fide telomeres. Strikingly, telomere-containing RNA accumulates extrachromosomally in gorilla mitotic cells, suggesting that at least some aspects of telomere-containing RNA biogenesis have diverged in gorilla, perhaps in concert with the evolution of heterochromatic caps in this species.

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Related in: MedlinePlus

Telomere repeats and the Cht7 minisatellite are physically linked on gorilla chromosomes and are co-transcribed. A PCR approach was adapted to determine whether Cht7 and telomeric sequences were physically linked and co-transcribed. A telomeric C-rich primer, ending with a unique 3′-end (C-telorette) was used to reverse transcribe total gorilla RNA (top). The unique sequence (C-teltail) was used to prime PCR reactions in combination with primers specific to Cht7-sequence, either in the sense (panF) or in the antisense (panR) orientation. PCR products were separated in a 1% agarose gel and hybridized with either digoxigenin-labeled telomeric C-rich probes (bottom left) or Cht7-oligo (bottom right). PCR templates included: lane 1: genomic DNA; lane 2: cDNA transcribed with C-telorette3; lane 3: same RNA sample treated as in 2 but leaving out the reverse transcriptase (RT); lane 4: same as in 3 but treated with DNAse I; lane 5: same as in 3 but treated with RNase I; and lane 6: RT reaction with no RNA. Both the telomeric and the Cht7 probes revealed amplified products from genomic DNA exclusively obtained with the combination C-teltail/panF, indicating proximity of both sequences and allowing orienting the minisatellite repeats with regard to the telomeric sequences. On the other hand, the Cht7 probe reveals rare molecules (arrows) amplified using the same couple of primers and the C-telorette cDNA, suggesting the presence of RNA molecules carrying both telomere and Cht7 repeats.
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gkt169-F6: Telomere repeats and the Cht7 minisatellite are physically linked on gorilla chromosomes and are co-transcribed. A PCR approach was adapted to determine whether Cht7 and telomeric sequences were physically linked and co-transcribed. A telomeric C-rich primer, ending with a unique 3′-end (C-telorette) was used to reverse transcribe total gorilla RNA (top). The unique sequence (C-teltail) was used to prime PCR reactions in combination with primers specific to Cht7-sequence, either in the sense (panF) or in the antisense (panR) orientation. PCR products were separated in a 1% agarose gel and hybridized with either digoxigenin-labeled telomeric C-rich probes (bottom left) or Cht7-oligo (bottom right). PCR templates included: lane 1: genomic DNA; lane 2: cDNA transcribed with C-telorette3; lane 3: same RNA sample treated as in 2 but leaving out the reverse transcriptase (RT); lane 4: same as in 3 but treated with DNAse I; lane 5: same as in 3 but treated with RNase I; and lane 6: RT reaction with no RNA. Both the telomeric and the Cht7 probes revealed amplified products from genomic DNA exclusively obtained with the combination C-teltail/panF, indicating proximity of both sequences and allowing orienting the minisatellite repeats with regard to the telomeric sequences. On the other hand, the Cht7 probe reveals rare molecules (arrows) amplified using the same couple of primers and the C-telorette cDNA, suggesting the presence of RNA molecules carrying both telomere and Cht7 repeats.

Mentions: Previously published data demonstrate that Cht7 minisatellite sequences are associated with the heterochromatic caps exclusive to chimpanzees and gorillas, and suggest that Cht7 may be physically connected to telomere repeats (21). A restriction fragment analysis by Southern blotting revealed that both telomere and Cht7 repeats are sensitive to Bal31 digestion, thus confirming their position close to a chromosome end (Supplementary Figure S4). Furthermore, PCR reactions using a C-telorette (partly complementary to telomere repeats) and one oligonucleotide representing the Cht7 repeat unit (here called panF) allowed the amplification, from genomic DNA, of molecules containing both telomeric and Cht7 repeats, further supporting the idea that these sequences are physically connected (Figure 6, left panel, lane 1). This physical proximity raised the possibility that both sequences may be co-transcribed.Figure 6.


The heterochromatic chromosome caps in great apes impact telomere metabolism.

Novo C, Arnoult N, Bordes WY, Castro-Vega L, Gibaud A, Dutrillaux B, Bacchetti S, Londoño-Vallejo A - Nucleic Acids Res. (2013)

Telomere repeats and the Cht7 minisatellite are physically linked on gorilla chromosomes and are co-transcribed. A PCR approach was adapted to determine whether Cht7 and telomeric sequences were physically linked and co-transcribed. A telomeric C-rich primer, ending with a unique 3′-end (C-telorette) was used to reverse transcribe total gorilla RNA (top). The unique sequence (C-teltail) was used to prime PCR reactions in combination with primers specific to Cht7-sequence, either in the sense (panF) or in the antisense (panR) orientation. PCR products were separated in a 1% agarose gel and hybridized with either digoxigenin-labeled telomeric C-rich probes (bottom left) or Cht7-oligo (bottom right). PCR templates included: lane 1: genomic DNA; lane 2: cDNA transcribed with C-telorette3; lane 3: same RNA sample treated as in 2 but leaving out the reverse transcriptase (RT); lane 4: same as in 3 but treated with DNAse I; lane 5: same as in 3 but treated with RNase I; and lane 6: RT reaction with no RNA. Both the telomeric and the Cht7 probes revealed amplified products from genomic DNA exclusively obtained with the combination C-teltail/panF, indicating proximity of both sequences and allowing orienting the minisatellite repeats with regard to the telomeric sequences. On the other hand, the Cht7 probe reveals rare molecules (arrows) amplified using the same couple of primers and the C-telorette cDNA, suggesting the presence of RNA molecules carrying both telomere and Cht7 repeats.
© Copyright Policy - creative-commons
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC3643582&req=5

gkt169-F6: Telomere repeats and the Cht7 minisatellite are physically linked on gorilla chromosomes and are co-transcribed. A PCR approach was adapted to determine whether Cht7 and telomeric sequences were physically linked and co-transcribed. A telomeric C-rich primer, ending with a unique 3′-end (C-telorette) was used to reverse transcribe total gorilla RNA (top). The unique sequence (C-teltail) was used to prime PCR reactions in combination with primers specific to Cht7-sequence, either in the sense (panF) or in the antisense (panR) orientation. PCR products were separated in a 1% agarose gel and hybridized with either digoxigenin-labeled telomeric C-rich probes (bottom left) or Cht7-oligo (bottom right). PCR templates included: lane 1: genomic DNA; lane 2: cDNA transcribed with C-telorette3; lane 3: same RNA sample treated as in 2 but leaving out the reverse transcriptase (RT); lane 4: same as in 3 but treated with DNAse I; lane 5: same as in 3 but treated with RNase I; and lane 6: RT reaction with no RNA. Both the telomeric and the Cht7 probes revealed amplified products from genomic DNA exclusively obtained with the combination C-teltail/panF, indicating proximity of both sequences and allowing orienting the minisatellite repeats with regard to the telomeric sequences. On the other hand, the Cht7 probe reveals rare molecules (arrows) amplified using the same couple of primers and the C-telorette cDNA, suggesting the presence of RNA molecules carrying both telomere and Cht7 repeats.
Mentions: Previously published data demonstrate that Cht7 minisatellite sequences are associated with the heterochromatic caps exclusive to chimpanzees and gorillas, and suggest that Cht7 may be physically connected to telomere repeats (21). A restriction fragment analysis by Southern blotting revealed that both telomere and Cht7 repeats are sensitive to Bal31 digestion, thus confirming their position close to a chromosome end (Supplementary Figure S4). Furthermore, PCR reactions using a C-telorette (partly complementary to telomere repeats) and one oligonucleotide representing the Cht7 repeat unit (here called panF) allowed the amplification, from genomic DNA, of molecules containing both telomeric and Cht7 repeats, further supporting the idea that these sequences are physically connected (Figure 6, left panel, lane 1). This physical proximity raised the possibility that both sequences may be co-transcribed.Figure 6.

Bottom Line: In contrast with the limited sequence divergence accumulated after separation of higher primate lineages, marked cytogenetic variation has been associated with the genome evolution in these species.Studying the impact of such structural variations on defined molecular processes can provide valuable insights on how genome structural organization contributes to organismal evolution.In gorilla, on the other hand, a proportion of the subtelomeric heterochromatic caps present in most chromosome arms are associated with large blocks of telomere-like sequences that follow a replication program different from that of bona fide telomeres.

View Article: PubMed Central - PubMed

Affiliation: Telomeres and Cancer laboratory, 'Equipe Labellisée Ligue contre le Cancer', UMR3244, Institut Curie, 26 rue d'Ulm, 75248 Paris, France.

ABSTRACT
In contrast with the limited sequence divergence accumulated after separation of higher primate lineages, marked cytogenetic variation has been associated with the genome evolution in these species. Studying the impact of such structural variations on defined molecular processes can provide valuable insights on how genome structural organization contributes to organismal evolution. Here, we show that telomeres on chromosome arms carrying subtelomeric heterochromatic caps in the chimpanzee, which are completely absent in humans, replicate later than telomeres on chromosome arms without caps. In gorilla, on the other hand, a proportion of the subtelomeric heterochromatic caps present in most chromosome arms are associated with large blocks of telomere-like sequences that follow a replication program different from that of bona fide telomeres. Strikingly, telomere-containing RNA accumulates extrachromosomally in gorilla mitotic cells, suggesting that at least some aspects of telomere-containing RNA biogenesis have diverged in gorilla, perhaps in concert with the evolution of heterochromatic caps in this species.

Show MeSH
Related in: MedlinePlus