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The Analysis of Pendolino (peo) Mutants Reveals Differences in the Fusigenic Potential among Drosophila Telomeres.

Cenci G, Ciapponi L, Marzullo M, Raffa GD, Morciano P, Raimondo D, Burla R, Saggio I, Gatti M - PLoS Genet. (2015)

Bottom Line: The Peo protein directly interacts with the terminin components, but peo mutations do not affect telomeric localization of HOAP, Moi, Ver and HP1a, suggesting that the peo-dependent telomere fusion phenotype is not due to loss of terminin from chromosome ends. peo mutants are also defective in DNA replication and PCNA recruitment.However, our results suggest that general defects in DNA replication are unable to induce TFs in Drosophila cells.We thus hypothesize that DNA replication in Peo-depleted cells results in specific fusigenic lesions concentrated in heterochromatin-associated telomeres.

View Article: PubMed Central - PubMed

Affiliation: Dipartimento di Biologia e Biotecnologie, Sapienza-Università di Roma, Roma, Italy; Istituto Pasteur Fondazione Cenci Bolognetti, Sapienza-Università di Roma, Roma, Italy.

ABSTRACT
Drosophila telomeres are sequence-independent structures that are maintained by transposition to chromosome ends of three specialized retroelements (HeT-A, TART and TAHRE; collectively designated as HTT) rather than telomerase activity. Fly telomeres are protected by the terminin complex (HOAP-HipHop-Moi-Ver) that localizes and functions exclusively at telomeres and by non-terminin proteins that do not serve telomere-specific functions. Although all Drosophila telomeres terminate with HTT arrays and are capped by terminin, they differ in the type of subtelomeric chromatin; the Y, XR, and 4L HTT are juxtaposed to constitutive heterochromatin, while the XL, 2L, 2R, 3L and 3R HTT are linked to the TAS repetitive sequences; the 4R HTT is associated with a chromatin that has features common to both euchromatin and heterochromatin. Here we show that mutations in pendolino (peo) cause telomeric fusions (TFs). The analysis of several peo mutant combinations showed that these TFs preferentially involve the Y, XR and 4th chromosome telomeres, a TF pattern never observed in the other 10 telomere-capping mutants so far characterized. peo encodes a non-terminin protein homologous to the E2 variant ubiquitin-conjugating enzymes. The Peo protein directly interacts with the terminin components, but peo mutations do not affect telomeric localization of HOAP, Moi, Ver and HP1a, suggesting that the peo-dependent telomere fusion phenotype is not due to loss of terminin from chromosome ends. peo mutants are also defective in DNA replication and PCNA recruitment. However, our results suggest that general defects in DNA replication are unable to induce TFs in Drosophila cells. We thus hypothesize that DNA replication in Peo-depleted cells results in specific fusigenic lesions concentrated in heterochromatin-associated telomeres. Alternatively, it is possible that Peo plays a dual function being independently required for DNA replication and telomere capping.

No MeSH data available.


Related in: MedlinePlus

Mutations in peo cause telomeric fusions.(A) Examples of TFs in peo mutant neuroblasts. (A1-2) Control (Oregon-R) male (A1) and female (A2) metaphases; (A3-A5) peo1/peo1 metaphases showing: (A3) a ring autosome (abbreviated with A; asterisk) and, starting from the arrow, a multicentric chromosome A-XL∙XR-4-4-XR∙XL-A-A; (A4) an XR-4 TF (arrowhead) and an A-A-A-A multicentric chromosome (arrow); (A5) a 4 (arrow)-XR∙XL-A-A-A-A-XL∙XR-4 multicentric chromosome including the entire female complement. (A6-A9) peoh/peoh metaphases showing: (A6) a ring Y chromosome (arrowhead) and a 4 (arrow)-4-XR tricentric chromosome; (A7) a 4 (arrow)-YS∙YL-XR tricentric chromosome; (A8) two 4-XR TFs (arrows); (A9) an XR-XR TF (arrow). (B) Frequencies of TFs in peo mutant combinations. hs-peo and peo-HA are rescued by a construct carrying a wild type copy of the peo gene. At least 250 cells from at least 4 brains were scored for each genotype. (C) Deficiency mapping of peo. (D) Complementation analysis showing the phenotypes of animals heterozygous for the indicated genes/alleles.
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pgen.1005260.g001: Mutations in peo cause telomeric fusions.(A) Examples of TFs in peo mutant neuroblasts. (A1-2) Control (Oregon-R) male (A1) and female (A2) metaphases; (A3-A5) peo1/peo1 metaphases showing: (A3) a ring autosome (abbreviated with A; asterisk) and, starting from the arrow, a multicentric chromosome A-XL∙XR-4-4-XR∙XL-A-A; (A4) an XR-4 TF (arrowhead) and an A-A-A-A multicentric chromosome (arrow); (A5) a 4 (arrow)-XR∙XL-A-A-A-A-XL∙XR-4 multicentric chromosome including the entire female complement. (A6-A9) peoh/peoh metaphases showing: (A6) a ring Y chromosome (arrowhead) and a 4 (arrow)-4-XR tricentric chromosome; (A7) a 4 (arrow)-YS∙YL-XR tricentric chromosome; (A8) two 4-XR TFs (arrows); (A9) an XR-XR TF (arrow). (B) Frequencies of TFs in peo mutant combinations. hs-peo and peo-HA are rescued by a construct carrying a wild type copy of the peo gene. At least 250 cells from at least 4 brains were scored for each genotype. (C) Deficiency mapping of peo. (D) Complementation analysis showing the phenotypes of animals heterozygous for the indicated genes/alleles.

Mentions: The pendolino1(peo1) mutation was isolated by a cytological screen of 120 late lethal mutants mapping to the second chromosome, recovered after I element mobilization by I-R dysgenic crosses (see Materials and Methods). Mitotic cells of DAPI-stained brain preparations from peo1/peo1 larvae displayed very frequent telomeric fusions (TFs; Fig 1A and 1B), often resulting in multicentric linear chromosomes that resemble little “trains” of chromosomes. The pendolino gene was named after this phenotype just as caravaggio, modigliani and verrocchio, which are all names of Italian trains.


The Analysis of Pendolino (peo) Mutants Reveals Differences in the Fusigenic Potential among Drosophila Telomeres.

Cenci G, Ciapponi L, Marzullo M, Raffa GD, Morciano P, Raimondo D, Burla R, Saggio I, Gatti M - PLoS Genet. (2015)

Mutations in peo cause telomeric fusions.(A) Examples of TFs in peo mutant neuroblasts. (A1-2) Control (Oregon-R) male (A1) and female (A2) metaphases; (A3-A5) peo1/peo1 metaphases showing: (A3) a ring autosome (abbreviated with A; asterisk) and, starting from the arrow, a multicentric chromosome A-XL∙XR-4-4-XR∙XL-A-A; (A4) an XR-4 TF (arrowhead) and an A-A-A-A multicentric chromosome (arrow); (A5) a 4 (arrow)-XR∙XL-A-A-A-A-XL∙XR-4 multicentric chromosome including the entire female complement. (A6-A9) peoh/peoh metaphases showing: (A6) a ring Y chromosome (arrowhead) and a 4 (arrow)-4-XR tricentric chromosome; (A7) a 4 (arrow)-YS∙YL-XR tricentric chromosome; (A8) two 4-XR TFs (arrows); (A9) an XR-XR TF (arrow). (B) Frequencies of TFs in peo mutant combinations. hs-peo and peo-HA are rescued by a construct carrying a wild type copy of the peo gene. At least 250 cells from at least 4 brains were scored for each genotype. (C) Deficiency mapping of peo. (D) Complementation analysis showing the phenotypes of animals heterozygous for the indicated genes/alleles.
© Copyright Policy
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4481407&req=5

pgen.1005260.g001: Mutations in peo cause telomeric fusions.(A) Examples of TFs in peo mutant neuroblasts. (A1-2) Control (Oregon-R) male (A1) and female (A2) metaphases; (A3-A5) peo1/peo1 metaphases showing: (A3) a ring autosome (abbreviated with A; asterisk) and, starting from the arrow, a multicentric chromosome A-XL∙XR-4-4-XR∙XL-A-A; (A4) an XR-4 TF (arrowhead) and an A-A-A-A multicentric chromosome (arrow); (A5) a 4 (arrow)-XR∙XL-A-A-A-A-XL∙XR-4 multicentric chromosome including the entire female complement. (A6-A9) peoh/peoh metaphases showing: (A6) a ring Y chromosome (arrowhead) and a 4 (arrow)-4-XR tricentric chromosome; (A7) a 4 (arrow)-YS∙YL-XR tricentric chromosome; (A8) two 4-XR TFs (arrows); (A9) an XR-XR TF (arrow). (B) Frequencies of TFs in peo mutant combinations. hs-peo and peo-HA are rescued by a construct carrying a wild type copy of the peo gene. At least 250 cells from at least 4 brains were scored for each genotype. (C) Deficiency mapping of peo. (D) Complementation analysis showing the phenotypes of animals heterozygous for the indicated genes/alleles.
Mentions: The pendolino1(peo1) mutation was isolated by a cytological screen of 120 late lethal mutants mapping to the second chromosome, recovered after I element mobilization by I-R dysgenic crosses (see Materials and Methods). Mitotic cells of DAPI-stained brain preparations from peo1/peo1 larvae displayed very frequent telomeric fusions (TFs; Fig 1A and 1B), often resulting in multicentric linear chromosomes that resemble little “trains” of chromosomes. The pendolino gene was named after this phenotype just as caravaggio, modigliani and verrocchio, which are all names of Italian trains.

Bottom Line: The Peo protein directly interacts with the terminin components, but peo mutations do not affect telomeric localization of HOAP, Moi, Ver and HP1a, suggesting that the peo-dependent telomere fusion phenotype is not due to loss of terminin from chromosome ends. peo mutants are also defective in DNA replication and PCNA recruitment.However, our results suggest that general defects in DNA replication are unable to induce TFs in Drosophila cells.We thus hypothesize that DNA replication in Peo-depleted cells results in specific fusigenic lesions concentrated in heterochromatin-associated telomeres.

View Article: PubMed Central - PubMed

Affiliation: Dipartimento di Biologia e Biotecnologie, Sapienza-Università di Roma, Roma, Italy; Istituto Pasteur Fondazione Cenci Bolognetti, Sapienza-Università di Roma, Roma, Italy.

ABSTRACT
Drosophila telomeres are sequence-independent structures that are maintained by transposition to chromosome ends of three specialized retroelements (HeT-A, TART and TAHRE; collectively designated as HTT) rather than telomerase activity. Fly telomeres are protected by the terminin complex (HOAP-HipHop-Moi-Ver) that localizes and functions exclusively at telomeres and by non-terminin proteins that do not serve telomere-specific functions. Although all Drosophila telomeres terminate with HTT arrays and are capped by terminin, they differ in the type of subtelomeric chromatin; the Y, XR, and 4L HTT are juxtaposed to constitutive heterochromatin, while the XL, 2L, 2R, 3L and 3R HTT are linked to the TAS repetitive sequences; the 4R HTT is associated with a chromatin that has features common to both euchromatin and heterochromatin. Here we show that mutations in pendolino (peo) cause telomeric fusions (TFs). The analysis of several peo mutant combinations showed that these TFs preferentially involve the Y, XR and 4th chromosome telomeres, a TF pattern never observed in the other 10 telomere-capping mutants so far characterized. peo encodes a non-terminin protein homologous to the E2 variant ubiquitin-conjugating enzymes. The Peo protein directly interacts with the terminin components, but peo mutations do not affect telomeric localization of HOAP, Moi, Ver and HP1a, suggesting that the peo-dependent telomere fusion phenotype is not due to loss of terminin from chromosome ends. peo mutants are also defective in DNA replication and PCNA recruitment. However, our results suggest that general defects in DNA replication are unable to induce TFs in Drosophila cells. We thus hypothesize that DNA replication in Peo-depleted cells results in specific fusigenic lesions concentrated in heterochromatin-associated telomeres. Alternatively, it is possible that Peo plays a dual function being independently required for DNA replication and telomere capping.

No MeSH data available.


Related in: MedlinePlus