Freezing-thawing induces alterations in histone H1-DNA binding and the breaking of protein-DNA disulfide bonds in boar sperm

E. Flores, L. Ramió-Lluch, D. Bucci, J. M. Fernández-Novell, A. Peña, J. E. Rodríguez-Gil, Teresa Josefa Rigau Mas

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51 Citations (Scopus)

Abstract

The main aim of this work is to gain insight into the mechanisms by which freezing-thawing alters the nucleoprotein structure of boar sperm. For this purpose, the freezing-thawing-related changes of structure and location of histones-DNA domains in the boar sperm head were analyzed through Western blot and immunocytochemistry. Afterwards, it was analyzed whether freezing-thawing induced changes in tyrosine phosphorylation levels of both protamine 1 and histone H1, through Western blot analyses in samples previously subjected to immunoprecipitation. This analysis was completed with the determination of the changes induced by freezing-thawing on the overall levels of sperm-head disulfide bonds through analysis of free-cysteine radicals levels. Freezing-thawing induced significant changes in the histones-DNA structures, which were manifested in the appearance of a freezing-thawing-linked histone H1-DNA aggregate of about a 35-kDa band and in the spreading of histone H1-positive markings from the caudal area of the sperm head to more cranial zones. Freezing-thawing did not have any significant effect on the tyrosine phosphorylation levels of either protamine 1 or histone H1. However, thawed samples showed a significant (P < 0.05) increase in the free cysteine radical content (from 3.1 ± 0.5nmol/μg protein in fresh samples to 6.7 ± 0.8 nmol/μg protein). In summary, our results suggest that freezing-thawing causes significant alterations in the nucleoprotein structure of boar sperm head by mechanism/s linked with the rupture of disulfide bonds among the DNA. These mechanisms seem to be unspecific, affecting both the protamines-DNA unions and the histones-DNA bonds in a similar way. Furthermore, results suggest that the boar-sperm nuclear structure is heterogeneous suggesting the existence of a zonated pattern, differing in their total DNA density and the compactness of the precise nucleoprotein structures present in each zone. © 2011 Elsevier Inc.
Original languageEnglish
Pages (from-to)1450-1464
JournalTheriogenology
Volume76
Issue number8
DOIs
Publication statusPublished - 1 Nov 2011

Keywords

  • Boar sperm
  • Disulfide bonds
  • Freezing-Thawing
  • Histone H1

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