title: The HMG-box-containing proteins tHMG-1 and tHMG-2 interact during the histone-to-protamine transition in Drosophila spermatogenesis.
abstract: Spermatogenesis is accompanied by a remarkable reorganization of the chromatin in post-meiotic stages, characterized by a near genome-wide displacement of histones by protamines and a transient expression of transition proteins. In Drosophila, the transition-protein-like protein Tpl94D contains an HMG-box domain and is expressed during chromatin reorganization. Here, we searched for additional HMG-box-containing proteins with a similar expression pattern. We identified two proteins specifically expressed in the testis, tHMG-1 and tHMG-2, whose expression levels were highest during the histone-to-protamine transition. Protein-protein interaction studies revealed that tHMG-1 and tHMG-2 form heterodimers in vivo. We demonstrated that Tpl94D, tHMG-1 and tHMG-2 localize to chromatin of the male germ line, with the most abundant levels observed during post-meiotic chromatin reorganization. Analysis of a tpl94D mutant showed that the C-terminal region of Tpl94D is dispensable for fertility. These data strongly suggested either that the truncated protein, which still contains the N-terminal HMG-box domain, is functional or that other proteins act in functional redundancy with Tpl94D during spermiogenesis. A thmg-1/thmg-2 null mutant also had no detectable specific phenotype, but hmgz, which encodes the major somatic HMG-box-containing protein HMGZ, was transcriptionally up-regulated. Our results showed that Drosophila spermatogenesis is characterized by continuous and overlapping expression of different HMG-box-containing proteins. We hypothesize that the mechanism of chromatin reorganization is a process highly secured by redundancies.
authors.affiliation: Philipps-Universität Marburg, Fachbereich Biologie, Entwicklungsbiologie, Karl-von-Frisch Straße 8, 35043 Marburg, Germany. Electronic address: stefanie.gaertner@biologie.uni-marburg.de.
authors.forename: Stefanie M K
authors.initials: SM
authors.lastname: Gärtner
authors.affiliation: Philipps-Universität Marburg, Fachbereich Biologie, Entwicklungsbiologie, Karl-von-Frisch Straße 8, 35043 Marburg, Germany. Electronic address: silke.rothenbusch@biologie.uni-marburg.de.
authors.forename: Silke
authors.initials: S
authors.lastname: Rothenbusch
authors.affiliation: Justus-Liebig-Universität Giessen, Institut für Genetik, Heinrich-Buff-Ring 58-62, 35392 Giessen, Germany. Electronic address: melanie.k.buxa@bio.uni-giessen.de.
authors.forename: Melanie K
authors.initials: MK
authors.lastname: Buxa
authors.affiliation: Philipps-Universität Marburg, Fachbereich Biologie, Entwicklungsbiologie, Karl-von-Frisch Straße 8, 35043 Marburg, Germany. Electronic address: ina.theofel@biologie.uni-marburg.de.
authors.forename: Ina
authors.initials: I
authors.lastname: Theofel
authors.affiliation: Justus-Liebig-Universität Giessen, Institut für Genetik, Heinrich-Buff-Ring 58-62, 35392 Giessen, Germany. Electronic address: rainer.renkawitz@gen.bio.uni-giessen.de.
authors.forename: Rainer
authors.initials: R
authors.lastname: Renkawitz
authors.affiliation: Philipps-Universität Marburg, Fachbereich Biologie, Entwicklungsbiologie, Karl-von-Frisch Straße 8, 35043 Marburg, Germany. Electronic address: rathke@biologie.uni-marburg.de.
authors.forename: Christina
authors.initials: C
authors.lastname: Rathke
authors.affiliation: Philipps-Universität Marburg, Fachbereich Biologie, Entwicklungsbiologie, Karl-von-Frisch Straße 8, 35043 Marburg, Germany. Electronic address: renkawit@biologie.uni-marburg.de.
authors.forename: Renate
authors.initials: R
authors.lastname: Renkawitz-Pohl
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D002843:Chromatin / Q000378:metabolism; D004331:Drosophila melanogaster / Q000235:genetics / Q000378:metabolism*; D024002:HMGB Proteins / Q000378:metabolism*; D006657:Histones / Q000378:metabolism*; D008297:Male; D011479:Protamines / Q000378:metabolism*; D013091:Spermatogenesis / Q000502:physiology*; D013737:Testis / Q000378:metabolism
chemical_list: D002843:Chromatin; D024002:HMGB Proteins; D006657:Histones; D011479:Protamines
keywords: Chromatin; Drosophila; HMG-box-containing protein; Histone-to-protamine transition; Spermatogenesis; Transition protein