ABSTRACT
In most animals, the extreme compaction of sperm DNA is achieved after the massive replacement of histones with sperm nuclear basic proteins (SNBPs), such as protamines. In some species, the ultracompact sperm chromatin is stabilized by a network of disulfide bonds connecting cysteine residues present in SNBPs. Studies in mammals have established that the reduction of these disulfide crosslinks at fertilization is required for sperm nuclear decondensation and the formation of the male pronucleus. Here, we show that the Drosophila maternal thioredoxin Deadhead (DHD) is specifically required to unlock sperm chromatin at fertilization. In dhd mutant eggs, the sperm nucleus fails to decondense and the replacement of SNBPs with maternally-provided histones is severely delayed, thus preventing the participation of paternal chromosomes in embryo development. We demonstrate that DHD localizes to the sperm nucleus to reduce its disulfide targets and is then rapidly degraded after fertilization.
Subject(s)
Chromatin/physiology , Drosophila Proteins/metabolism , Drosophila melanogaster/metabolism , Fertilization/physiology , Membrane Proteins/metabolism , Ovum/physiology , Spermatozoa/physiology , Thioredoxins/metabolism , Animals , Drosophila Proteins/genetics , Drosophila melanogaster/embryology , Female , Gene Expression Regulation/physiology , Male , Membrane Proteins/genetics , Thioredoxins/geneticsABSTRACT
During spermiogenesis, histones are massively replaced with protamines. A previous report showed that Drosophila males homozygous for a genomic deletion covering several genes including the protamine-like genes Mst35Ba/b are surprisingly fertile. Here, we have precisely deleted the Mst35B locus by homologous recombination, and we confirm the dispensability of Mst35Ba/b for fertility.
Subject(s)
Drosophila Proteins/genetics , Drosophila/genetics , Infertility, Male/genetics , Protamines/genetics , Spermatozoa/cytology , Amino Acid Sequence , Animals , Drosophila/physiology , Gene Deletion , Male , Molecular Sequence DataABSTRACT
Viruses represent an important cause of cancer in humans: infections are estimated to account for close to one cancer case out of five.With the ongoing discovery of new infectious agents, this number should be raising in the near future. In 2006, the discovery of a new _-retrovirus in prostate cancer biopsies launched an intense research activity: could this new xenotropic MLV-related virus (XMRV) be the cause of prostate cancer? Five years later, the initial enthusiasm of retrovirologists has dramatically diminished. One by one, arguments favouring the hypothesis of human infection with XMRV are being refuted. The aim of this review article is to present the discovery of XMRV and to analyze recent data arguing against its existence in humans. A synthetic interpretation of XMRV literature will then be suggested.
