Molecular organization of internal telomeric sequences in Chinese hamster chromosomes

Faravelli, M; Azzalin, Claus M.; Bertoni, Livia; Chernova, Olga B.; Attolini, Carmen; Mondello, Chiara; Giulotto, Elena

doi:10.1016/s0378-1119(01)00877-0

Cited by 48 publications

(55 citation statements)

References 29 publications

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“…Some relatively short ITS in Chinese hamster genome are flanked by retroelement sequences (93) but we found that at least some of these elements adjacent to tandem arrays of TTAGGG are extensively transcribed. (96) This indicates that TTAGGG repeats do not generally work as transcription silencers of adjacent genes in cis but the question of how low-level transcription of ITS itself is maintained remains unanswered.…”

Section: Global Sine Clustering and Line Depletion In Gc-rich Gene-rimentioning

confidence: 74%

“…(92) ITS may contain slightly diverged TTAGGG repeats but, in the Chinese hamster genome, many of them do not have internal sites for restriction nuclease HindIII and are associated with long (>100 kb) gene-free arrays hybridizing to telomeric probes. (93) The reasons for the apparent instability of ITS are unknown. We found that downregulation of endogenous TTAGGGbinding protein TRF1 increases the frequency of spontaneous chromosome aberrations in Chinese hamster cells (94) but the mechanism remains unknown.…”

Section: Global Sine Clustering and Line Depletion In Gc-rich Gene-rimentioning

confidence: 99%

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Regulation of mammalian gene expression by retroelements and non‐coding tandem repeats

Tomilin

2008

BioEssays

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Genomes of higher eukaryotes contain abundant non‐coding repeated sequences whose overall biological impact is unclear. They comprise two categories. The first consists of retrotransposon‐derived elements. These are three major families of retroelements (LINEs, SINEs and LTRs). SINEs are clustered in gene‐rich regions and are found in promoters of genes while LINEs are concentrated in gene‐poor regions and are depleted from promoters. The second class consists of non‐coding tandem repeats (satellite DNAs and TTAGGG arrays), which are associated with mammalian centromeres, heterochromatin and telomeres. Terminal TTAGGG arrays are involved in telomere capping and satellite DNAs are located in heterochromatin, which is implicated in transcription silencing by gene repositioning (relocalization). It is unknown whether interstitial TTAGGG sequences, which are present in many vertebrates, have a function. Here, evidence will be presented that retroelements and TTAGGG arrays are involved in regulation of gene expression. Retroelements can provide binding sites for transcription factors and protect promoter CpG islands from repressive chromatin modifications, and may be also involved in nuclear compartmentalization of transcriptionally active and inactive domains. Interstitial telomere‐like sequences can form dynamically maintained three‐dimensional nuclear networks of transcriptionally inactive domains, which may be involved in transcription silencing like classic heterochromatin. BioEssays 30:338–348, 2008. © 2008 Wiley Periodicals, Inc.

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Section: Global Sine Clustering and Line Depletion In Gc-rich Gene-rimentioning

confidence: 74%

Section: Global Sine Clustering and Line Depletion In Gc-rich Gene-rimentioning

confidence: 99%

Regulation of mammalian gene expression by retroelements and non‐coding tandem repeats

Tomilin

2008

BioEssays

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“…Chinese hamster internal chromosome bands enriched in (TTAGGG)n repeats are interspersed with AT-rich sequences (Faravelli et al, 2002) and it has been suggested that these bands can arise during DSB repair because of nonhomologous integration of episomal telomeric repeats into unstable AT-rich DNA (Azzalin et al, 2001;Faravelli et al, 2002). AT-rich DNA may be frequently cleaved by endonuclease encoded by retrotransposons of L1 family (Jurka, 1997).…”

Section: Discussionmentioning

confidence: 99%

“…These nontelomeric internal (TTAGGG)n sequences (ITs) in Chinese hamster represent about 5% of all genome (Day et al, 1998). It has been recently shown that Chinese hamster ITs are composed of extensive and essentially continuous arrays of (TTAGGG)n repeats interspersed with AT-rich DNA and retroposons (Faravelli et al, 2002). Chromosome bands containing these arrays are known to be hot spots of radiationinduced and spontaneous chromosome rearrangements in cultivated cells (Alvarez et al, 1993;Fernandez et al, 1995;Bertoni et al, 1996;Slijepcevic et al, 1996;Day et al, 1998;Morgan et al, 2002) and introduction of (TTAGGG)n repeats into a mammallain gene leads to frequent chromosome rearrangements involving these repeats (Kilburn et al, 2001).…”

Section: Introductionmentioning

confidence: 99%

Protection of internal (TTAGGG)n repeats in Chinese hamster cells by telomeric protein TRF1

et al. 2003

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Chinese hamster cells have large interstitial (TTAGGG) bands (ITs) which are unstable and should be protected by an unknown mechanism. Here, we expressed in Chinese hamster V79 cells green fluorescent protein (GFP)-tagged human TRF1, and found that a major fraction of GFP-TRF1 bound to ITs is diffusionally mobile. This fraction strongly decreases after treatment of cells with wortmannin, a protein kinase inhibitor, and this drug also increases the frequency of chromosome aberrations. Ionizing radiation does not induce detectable translocation of GFP-TRF1 to the sites of random double-strand breaks visualized using antibodies against histone c-H2AX. TRF1 is known to be eliminated from telomeres by overexpression of tankyrase 1 which induces TRF1 poly(ADP-ribosyl)ation. We transfected V79 cells by plasmid encoding tankyrase 1 and found that the frequency of chromosome rearrangements is increased in these cells independently of their treatment by IR. Taken together, our results suggest that TRF1 is involved in sequence-specific protection of internal nontelomeric (TTAGGG)n repeats.

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“…Although this association has not yet been clarified, there are suggestions that it might indicate that the sequence (T 2 AG 3 ) n is a component of the centromeric repeats (Metcalf et al, 1997(Metcalf et al, , 1998. The presence of the sequence (T 2 AG 3 ) n in interstitial regions has been interpreted as a result of saltatory replications and insertions at intrachromosomal sites through the repair of double-strained breaks occurred in the germline during evolution (Pathak et al, 1995(Pathak et al, , 1998Azzalin et al, 2001;Faravelli et al, 2002). Despite the coincident localization of the telomeric repeat and heterochromatin, not all heterochromatic regions of bat chromosomes, nor of other vertebrate species, hybridize with telomeric DNA (Fontana et al, 1998;Gornung et al, 1998;Finato et al, 2000;Multani et al, 2001;Castiglia et al, 2002).…”

Section: Introductionmentioning

confidence: 99%

In situ hybridization of bat chromosomes with human (TTAGGG)n probe, after previous digestion with Alu I

Faria

Morielle‐Versute

2002

Genet. Mol. Biol.

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The purpose of this work was to verify the ability of the enzyme Alu I to cleave and/or remove satellite DNA sequences from heterochromatic regions in chromosomes of bats, by identifying the occurrence of modifications in the pattern of fluorescence in situ hybridization with telomeric DNA. The localization and fluorescence intensity of the telomeric DNA sites of the Alu-digested and undigested chromosomes of species Eumops glaucinus, Carollia perspicillata, and Platyrrhinus lineatus were analyzed. Telomeric sequences were detected at the termini of chromosomes of all three species, although, in C. perspicillata, the signals were very faint or absent in most chromosomes. This finding was interpreted as being due to a reduced number of copies of the telomeric repeat, resulting from extensive telomeric association and/or rearrangements undergone by the chromosomes of Carollia. Fluorescent signals were also observed in centromeric and pericentromeric regions in several two-arm chromosomes of E. glaucinus and C. perspicillata. In E. glaucinus and P. lineatus, some interstitial and terminal telomeric sites were observed to be in association with regions of constitutive heterochromatin and ribosomal DNA (NORs). After digestion, these telomeric sites showed a significant decrease in signal intensity, indicating that enzyme Alu I cleaves and/or removes part of the satellite DNA present in these regions. These results suggest that the telomeric sequence is a component of the heterochromatin, and that the C-band-positive regions of bat chromosomes have a different DNA composition.

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Molecular organization of internal telomeric sequences in Chinese hamster chromosomes

Cited by 48 publications

References 29 publications

Regulation of mammalian gene expression by retroelements and non‐coding tandem repeats

Regulation of mammalian gene expression by retroelements and non‐coding tandem repeats

Protection of internal (TTAGGG)n repeats in Chinese hamster cells by telomeric protein TRF1

In situ hybridization of bat chromosomes with human (TTAGGG)n probe, after previous digestion with Alu I

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