The Drosophila chromosomal protein Mst77F is processed to generate an essential component of mature sperm chromatin.
In most animals, the bulk of sperm DNA is packaged with sperm nuclear basic proteins (SNBPs), a diverse group of highly basic chromosomal proteins notably comprising mammalian protamines. The replacement of histones with SNBPs during spermiogenesis allows sperm DNA to reach an extreme level of compaction, but little is known about how SNBPs actually function in vivo Mst77F is a Drosophila SNBP with unique DNA condensation properties in vitro, but its role during spermiogenesis remains unclear. Here, we show that Mst77F is required for the compaction of sperm DNA and the production of mature sperm, through its cooperation with protamine-like proteins Mst35Ba/b. We demonstrate that Mst77F is incorporated in spermatid chromatin as a precursor protein, which is subsequently processed through the proteolysis of its N-terminus. The cleavage of Mst77F is very similar to the processing of protamine P2 during human spermiogenesis and notably leaves the cysteine residues in the mature protein intact, suggesting that they participate in the formation of disulfide cross-links. Despite the rapid evolution of SNBPs, sperm chromatin condensation thus involves remarkably convergent mechanisms in distantly related animals.
Laboratoire de Biométrie et Biologie Evolutive, CNRS UMR5558, University of Lyon, Université Claude Bernard Lyon 1, Villeurbanne, France shuhei.kimura@univ-lyon1.fr.
Shuhei
0000-0002-7674-7827
S
Kimura
Laboratoire de Biométrie et Biologie Evolutive, CNRS UMR5558, University of Lyon, Université Claude Bernard Lyon 1, Villeurbanne, France benjamin.loppin@univ-lyon1.fr.
Benjamin
0000-0002-7166-9233
B
Loppin
D000818:Animals; D002843:Chromatin / Q000235:genetics* / Q000378:metabolism; D042002:Chromatin Assembly and Disassembly; D029721:Drosophila Proteins / Q000737:chemistry / Q000378:metabolism*; D004331:Drosophila melanogaster; D006657:Histones / Q000737:chemistry / Q000378:metabolism*; D008297:Male; D011479:Protamines / Q000378:metabolism*; D059748:Proteolysis; D013091:Spermatogenesis; D013094:Spermatozoa / Q000378:metabolism*
D002843:Chromatin; D029721:Drosophila Proteins; D006657:Histones; C503323:Mst77F protein, Drosophila; C503324:ProtB protein, Drosophila; D011479:Protamines
Mst77F; convergent evolution; genome compaction; protamine; protein processing; spermiogenesis