106. NUCLEOSOME RETENTION DURING CHROMATIN PACKAGING IN HUMAN SPERMATOZOA
S. D. Roman A B , A. T. Reid A B , K. McEwan A , D. M. Campbell A B and D. A. Jans B CA Biology, University of Newcastle, Callaghan, Australia.
B ARC Centre of Excellence in Biotechnology & Development, NSW, Australia.
C Dept of Biochemistry & Molecular Biology, Monash University, Clayton, VIC, Australia.
Reproduction, Fertility and Development 22(9) 24-24 https://doi.org/10.1071/SRB10Abs106
Published: 6 September 2010
Abstract
In contrast to the histone packaging of somatic cells, spermatozoa are predominantly packaged by the protamine proteins. However, human spermatozoa retain ~15% histone packaging. Regions that are left nucleosome bound could be: either genes that are active shortly after fertilisation or genes that are transcribed late during spermatogenesis. DNA damage at histone bound loci would be of consequence to spermatogenesis and/or to a resulting embryo post-fertilisation. Western blot analysis confirmed the presence of acetylated H3 and H4 in sperm. Interestingly, we identified the presence of these modified histones in isolated good quality sperm considered to have complete packaging. This indicates that histone retention is not a consequence of aberrant chromatin remodelling. Using a combination of ChIP (chromatin immunoprecipitation) and tiling arrays we have identified regions bound by acetylated histone 3 (H3). ChIP-PCR confirmed histone retention at several of these loci. For the previously identified loci in exon 1 of the TNP-2 gene we were able to narrow the region bound to the size of one nucleosome only. Using a modified form of ChIP known as carrier ChIP we examined histone retention in individual ejaculates. We demonstrate that humans consistently retain acetylated H3 at the same loci. Retention of one nucleosome at the TNP-2 loci was maintained across ejaculates and donors. In conclusion, retention of acetylated H3 is consistently maintained during packaging of the genome in spermiogenesis.
