Telomeres are nucleoprotein complexes that protect the ends of linear chromosomes and regulate terminal DNA replication. If telomeres are not properly capped, they are sensed as double-strand breaks, leading to the activation of cell cycle checkpoints and inappropriate DNA repair, which might result in end-to-end fusions (Palm and de Lange 2008). In most organisms, telomeres contain arrays of GC-rich repeats, which are added to chromosome ends by telomerase (Palm and de Lange 2008). Drosophila telomeres are elongated by transposition of three specialized retroelements, rather than telomerase activity; several studies indicate that Drosophila telomeres are epigenetic structures assembled independently of the sequence of terminal DNA (Cenci et al. 2005; Mason et al. 2008; Rong 2008). In organisms with telomerase, telomeres are protected by two well-characterized protein assemblies: the Cdc13–Stn1–Ten1 (CST) and shelterin complexes. These complexes are evolutionarily conserved, even if they vary in composition and architecture in different phyla. The three subunits of the CST complex all contain oligonucleotide/oligosaccharide-binding (OB) fold domains, and interact to each other to form an RPA-like complex that binds the telomere 3′ overhang. (Mitton-Fry et al. 2002; Gao et al. 2007; Gelinas et al. 2009; Sun et al. 2009). Shelterin has been thoroughly characterized in human cells; it is a six-protein complex that specifically associates with the telomeric TTAGGG repeats. Three of the shelterin subunits interact directly with the TTAGGG repeats: TRF1 and TRF2 bind the TTAGGG duplex, and POT1 binds the 3′ overhang. TRF1, TRF2, and POT1 are interconnected by TIN2 and TPP1, and TRF2 interacts with hRap1, a distant homolog of Saccharomyces cerevisiae Rap1. The shelterin subunits share three properties that distinguish them from the nonshelterin telomere-associated proteins. They are specifically enriched at telomeres, they are present at telomeres throughout the cell cycle, and their functions are limited to telomere maintenance (Palm and de Lange 2008). The Stn1 and Ten1 subunits of the S. cerevisiae CST complex are conserved in Schizosaccharomyces pombe, plants, and humans, while shelterin-like elements are found in S. pombe and plants but not in S. cerevisiae (Martin et al. 2007; Song et al. 2008; Linger and Price 2009; Lue 2009; Miyake et al. 2009; Surovtseva et al. 2009). S. pombe and plants have both a shelterin-like complex and a CST-like complex, both of which are required for telomere protection. The two complexes are present also in humans, and are thought to collaborate in telomere protection. However, the human CST complex does not share the shelterin properties, and appears to have a relatively minor role in telomere capping. (Miyake et al. 2009; Surovtseva et al. 2009). In addition to the shelterin and CST components, yeast, plant, and mammalian telomeres contain several conserved polypeptides required for proper telomere function. These polypeptides include many proteins involved in DNA repair, such as the ATM kinase, the Ku70/80 heterodimer, the MRE11/RAD50/NBS1 (MRN) complex, Rad51, the ERCC1/XPF endonuclease, the Apollo exonuclease, and the RecQ family members WRN and BLM. In addition, yeast and mammalian telomeres are enriched in proteins that are homologous to Drosophila HP1 (Heterochromatin Protein 1). All nonshelterin and non-CST proteins function not only at telomeres, but are also involved in several cellular processes that are not related with telomeres (Palm and de Lange 2008; Linger and Price 2009). The search for Drosophila telomere-capping proteins has relied mainly on the isolation of mutants that display frequent telomeric fusions in larval brain cells. Genetic and molecular analyses thus far have identified nine loci that are required to prevent end-to-end fusion in Drosophila. These are UbcD1, which encodes a highly conserved E2 enzyme that mediates protein ubiquitination; Su(var)205 and caravaggio (cav), which encode HP1 and HOAP (HP1/origin recognition complex [ORC]-associated protein), respectively; the Drosophila homologs of the ATM, RAD50, MRE11, and NBS1 genes; without children (woc), which specifies a transcription factor associated with the initiating form of RNA polymerase II (Pol II); and modigliani (moi, which encodes a novel protein that binds both HOAP and HP1 (for review, see Cenci et al. 2005; Ciapponi and Cenci 2008; Mason et al. 2008; Rong 2008; see also Raffa et al. 2009). HOAP and Moi have properties that distinguish them from the other Drosophila telomere-capping proteins: They localize only at telomeres, and appear to function only in telomere maintenance. These properties are similar to the properties of human shelterin, suggesting that the HOAP–Moi complex, which we called terminin, is a functional analog of shelterin (Raffa et al. 2009). Here we show that Verrocchio (Ver) is required to prevent telomere fusion. Ver interacts directly with both HOAP and Moi and localizes only at telomeres, suggesting that Ver is a novel terminin component. Bioinformatics analyses showed that Ver contains an OB fold domain that shares structural similarity with the OB fold of Stn1. Mutations in the predicted Ver OB fold cause telomere fusion, suggesting that the Ver OB fold is required for telomere protection.