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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

Structure of the peo (CG10536) transcripts and available cDNAs.The triangles indicate P element insertions; P[PZ]05704 is not responsible for the crossbronx (cbx) phenotype (see text for detailed explanation). The Ntmt and CG18446 genes are nested into the introns defined by the peo-RA and peo-RC transcripts. The asterisks indicate the positions of ATG start codons.
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pgen.1005260.g002: Structure of the peo (CG10536) transcripts and available cDNAs.The triangles indicate P element insertions; P[PZ]05704 is not responsible for the crossbronx (cbx) phenotype (see text for detailed explanation). The Ntmt and CG18446 genes are nested into the introns defined by the peo-RA and peo-RC transcripts. The asterisks indicate the positions of ATG start codons.

Mentions: To identify the peo gene at the molecular level we exploited the peop112 allele that carries a P{w+, ry+}construct inserted into the gene [30]. Using inverse PCR we found that the P construct is inserted into the 5’ UTR of the longest transcript of the CG10536 gene (Fig 2). CG10536 was originally named ms(2)46C [32] an then renamed crossbronx (cbx) [33]. However, CG10536 does not correspond to ms(2)46C/cbx. The phenotype associated with the ms(2)46C/cbx mutation was attributed to the P{PZ}05704 insertion that maps just proximal to the UTR region of CG10536 (Fig 2). However, this attribution was only tentative because the male sterile phenotype was neither mapped over deficiency nor reverted by P element excision [32]. We found that males homozygous for the P{PZ}05704 insertion are sterile and show the spermatid abnormalities previously described [32]. In contrast, males bearing the same insertion over Df(2R)B5 that uncover the 46B-C interval were fully fertile and displayed normal spermatids (Fig 1D). We thus conclude that the ms(2)46C/cbx mutation maps outside the 46B-C region, and that CG10536 actually corresponds to pendolino.


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)

Structure of the peo (CG10536) transcripts and available cDNAs.The triangles indicate P element insertions; P[PZ]05704 is not responsible for the crossbronx (cbx) phenotype (see text for detailed explanation). The Ntmt and CG18446 genes are nested into the introns defined by the peo-RA and peo-RC transcripts. The asterisks indicate the positions of ATG start codons.
© Copyright Policy
Related In: Results  -  Collection

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

pgen.1005260.g002: Structure of the peo (CG10536) transcripts and available cDNAs.The triangles indicate P element insertions; P[PZ]05704 is not responsible for the crossbronx (cbx) phenotype (see text for detailed explanation). The Ntmt and CG18446 genes are nested into the introns defined by the peo-RA and peo-RC transcripts. The asterisks indicate the positions of ATG start codons.
Mentions: To identify the peo gene at the molecular level we exploited the peop112 allele that carries a P{w+, ry+}construct inserted into the gene [30]. Using inverse PCR we found that the P construct is inserted into the 5’ UTR of the longest transcript of the CG10536 gene (Fig 2). CG10536 was originally named ms(2)46C [32] an then renamed crossbronx (cbx) [33]. However, CG10536 does not correspond to ms(2)46C/cbx. The phenotype associated with the ms(2)46C/cbx mutation was attributed to the P{PZ}05704 insertion that maps just proximal to the UTR region of CG10536 (Fig 2). However, this attribution was only tentative because the male sterile phenotype was neither mapped over deficiency nor reverted by P element excision [32]. We found that males homozygous for the P{PZ}05704 insertion are sterile and show the spermatid abnormalities previously described [32]. In contrast, males bearing the same insertion over Df(2R)B5 that uncover the 46B-C interval were fully fertile and displayed normal spermatids (Fig 1D). We thus conclude that the ms(2)46C/cbx mutation maps outside the 46B-C region, and that CG10536 actually corresponds to pendolino.

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