title: Drosophila melanogaster kl-3 and kl-5 Y-loops harbor triple-stranded nucleic acids.
abstract: Primary spermatocyte nuclei of Drosophila melanogaster contain three prominent lampbrush-like loops. The development of these structures has been associated with the transcription of three fertility factors located on the Y chromosome, named kl-5, kl-3 and ks-1. These loci have huge physical dimensions and contain extremely long introns. In addition, kl-3 and kl-5 were shown to encode two putative dynein subunits required for the correct assembly of the sperm axoneme. Here, we show that both the kl-5 and kl-3 loops are intensely decorated by monoclonal antibodies recognizing triple-stranded nucleic acids, and that each loop presents a peculiar molecular organization of triplex structures. Moreover, immunostaining of Drosophila hydei primary spermatocytes revealed that also in this species - which diverged from D. melanogaster 58 million years ago - Y-loops are decorated by anti-triplex antibodies, strongly suggesting a conserved role of loop-associated triplexes. Finally, we showed that in D. melanogaster wild-type lines that are raised at the non-permissive temperature of 31+/-0.5 degrees C (which is known to induce male sterility in flies) both the triplex immunostaining and the axonemal dynein heavy chains encoded by kl-3 and kl-5 are no longer detectable, which suggests a functional correlation between loop-associated triplexes, the presence of axonemal proteins and male fertility in fly.
authors.affiliation: Department of Genetics and Molecular Biology - Sapienza Università di Roma, 00185 Rome, Italy. roberto.piergentili@uniroma1.it
authors.forename: Roberto
authors.initials: R
authors.lastname: Piergentili
authors.forename: Caterina
authors.initials: C
authors.lastname: Mencarelli
mesh_terms: D000818:Animals; D002467:Cell Nucleus / Q000737:chemistry / Q000235:genetics*; D004247:DNA / Q000737:chemistry*; D029721:Drosophila Proteins / Q000737:chemistry; D004331:Drosophila melanogaster / Q000737:chemistry / Q000166:cytology / Q000235:genetics*; D004398:Dyneins / Q000737:chemistry; D007438:Introns; D008297:Male; D009690:Nucleic Acid Conformation; D013090:Spermatocytes / Q000737:chemistry* / Q000648:ultrastructure; D014998:Y Chromosome / Q000235:genetics*
chemical_list: D029721:Drosophila Proteins; C051802:triplex DNA; D004247:DNA; D004398:Dyneins