Protection ofDrosophilachromosome ends through minimal telomere capping

Abstract

In Drosophila, telomere-capping proteins have the remarkable capacity to recognize chromosome ends in a sequence-independent manner. This epigenetic protection is essential to prevent catastrophic ligations of chromosome extremities. Interestingly, capping proteins occupy a large telomere chromatin domain of several kilobases; however, the functional relevance of this to end protection is unknown. Here, we investigate the role of the large capping domain by manipulating HOAP (encoded by caravaggio) capping-protein expression in the male germ cells, where telomere protection can be challenged without compromising viability. We show that the exhaustion of HOAP results in a dramatic reduction of other capping proteins at telomeres, including K81 [encoded by ms(3)K81], which is essential for male fertility. Strikingly however, we demonstrate that, although capping complexes are barely detected in HOAP-depleted male germ cells, telomere protection and male fertility are not dramatically affected. Our study thus demonstrates that efficient protection of Drosophila telomeres can be achieved with surprisingly low amounts of capping complexes. We propose that these complexes prevent fusions by acting at the very extremity of chromosomes, reminiscent of the protection conferred by extremely short telomeric arrays in yeast or mammalian systems.

Chromosome Healing Is Promoted by the Telomere Cap Component Hiphop inDrosophila

“…Our findings, that hiphop or ms(3)K81 overexpression promotes survival of cells with broken chromosomes, and, more critically, that hiphop overexpression promotes healing of broken chromosome ends in the male germline, provide strong support for the model that one role of Hiphop (and K81) is to seed telomere formation. The hypothesis that Hiphop plays a critical role in recruiting other telomere capping proteins is further supported by recent results showing that overexpression of Hiphop in the male germline is accompanied by increased localization of HOAP and HP1 to telomeres (Dubruille and Loppin 2015).…”

The Deadbeat Paternal Effect of Uncapped Sperm Telomeres on Cell Cycle Progression and Chromosome Behavior in Drosophila melanogaster

“…We assayed K81, which is present on meiotic telomeres and retained postmeiotically (Gao et al 2011;Dubruille and Loppin 2015). We observed the expected pattern of GFP-K81 foci in control spermatids.…”

“…However, in the melanogaster group species, HipHop has a testis-specific paralog called K81 (Dubruille et al 2010;Gao et al 2011). In D. melanogaster, K81 replaces HipHop in early meiosis and k81 mutant males produce sperm lacking TCCs (Dubruille et al 2010;Gao et al 2011;Dubruille and Loppin 2015). The consequence is male sterility due to a perplexing paternal effect (Fuyama 1984).…”

The hpRNA/RNAi Pathway Is Essential to Resolve Intragenomic Conflict in the Drosophila Male Germline

“…For each mutant genotype, 0–4 day old DsRed positive males were dissected and the mutant testes were recognized with the empty seminal vesicle and disrupted spermatogenesis. Whole-mount testes were stained as described (Dubruille and Loppin, 2015). Briefly, testes were dissected in PBS-T (1× PBS with 0.15% Triton), fixed in 4% formaldehyde 1× PBS for 20 min, washed 3 times in PBS-T before 4°C overnight incubation in primary antibodies.…”