Verrocchio, a Drosophila OB fold-containing protein, is a component of the terminin telomere-capping complex

Abstract

Drosophila telomeres are elongated by transposition of specialized retroelements rather than telomerase activity, and are assembled independently of the terminal DNA sequence. Drosophila telomeres are protected by terminin, a complex that includes the HOAP (Heterochromatin Protein 1/origin recognition complex-associated protein) and Moi (Modigliani) proteins and shares the properties of human shelterin. Here we show that Verrocchio (Ver), an oligonucleotide/oligosaccharide-binding (OB) fold-containing protein related to Rpa2/Stn1, interacts physically with HOAP and Moi, is enriched only at telomeres, and prevents telomere fusion. These results indicate that Ver is a new terminin component; we speculate that, concomitant with telomerase loss, Drosophila evolved terminin to bind chromosome ends independently of the DNA sequence.Supplemental material is available at http://www.genesdev.org.

Terminin: A protein complex that mediates epigenetic maintenance ofDrosophilatelomeres

“…However, GFP-Moi and Ver-GFP could not be detected at mitotic chromosome ends, probably due to their very low abundance. 31,32 These results indicate that HOAP, Moi and Ver form a complex that accumulates only at telomeres of both interphase (polytene) and mitotic chromosomes. In addition, available data indicate that HOAP, Moi and Ver function primarily if not exclusively at telomeres.…”

“…48 Ver contains an OB-fold domain that shares structural similarity with the OB fold domain of Rpa2/Stn1 and binds single stranded DNAs of different sequence (reviewed in ref. 32; our unpublished results). Substitution of four critical amino acids in the Ver OB fold abolished the DNA binding ability of the protein (our unpublished results).…”

“…32 An additional protein required to prevent telomere fusion, called HP1-HOAP interacting protein (or HipHop), was recently identified among the polypeptides that co-precipitate with HOAP. 20 Mutations in caravaggio (HOAP), modigliani and verrocchio cause very high frequencies of TFs (~5 per cell), often producing multicentric linear chromosomes that resemble little "trains" of chromosomes.…”

Mutations inCog7affect Golgi structure, meiotic cytokinesis and sperm development duringDrosophilaspermatogenesis

“…To generate the GFP-Cog7 construct, the EGFP CDS was fused in frame to the Nterminus of the full length CG31040 cDNA and cloned into the transformation vector pJZ4 (provided by G. D. Raffa;Raffa et al, 2010) under the control of a tubulin promoter. The Gateway strategy (Invitrogen) was used to generate the UAS-gio-RFP construct; full length gio cDNA was cloned into the transformation vector pPWR (DGRC, Indiana University) that contains the Gateway cassette, the UASp promoter and the C-terminal monomeric red fluorescent protein (mRFP) sequence.…”

Telomere Maintenance in Organisms without Telomerase

“…The telomere-specific components of the cap in Drosophila are collectively termed 'terminin' by analogy to the shelterin protein complex at mammalian telomeres (Raffa et al, 2009). The terminin proteins differ from the shelterin proteins, in part because the TRF1 and TRF2 components of shelterin bind specifically to the canonical telomeric repeat, while the formation of the telomere cap in Drosophila is sequence independent, and in part because many of the terminin proteins are among the fastest evolving proteins in Drosophila (Gao et al, 2010;Raffa et al, 2010;Schmid & Tautz, 1997). There is no direct evidence that the cap in Drosophila plays a role in maintaining chromosome length.…”