The characterization of amphibian nucleoplasmins yields new insight into their role in sperm chromatin remodeling
Date
2006-04-28
Authors
Frehlick, Lindsay J
Eirín-López, José María
Jeffery, Erin D
Hunt, Donald F
Ausió, Juan
Journal Title
Journal ISSN
Volume Title
Publisher
BioMed Central
Abstract
Background: Nucleoplasmin is a nuclear chaperone protein that has been shown to participate
in the remodeling of sperm chromatin immediately after fertilization by displacing highly specialized
sperm nuclear basic proteins (SNBPs), such as protamine (P type) and protamine-like (PL type)
proteins, from the sperm chromatin and by the transfer of histone H2A-H2B. The presence of
SNBPs of the histone type (H type) in some organisms (very similar to the histones found in somatic
tissues) raises uncertainty about the need for a nucleoplasmin-mediated removal process in such
cases and poses a very interesting question regarding the appearance and further differentiation of
the sperm chromatin remodeling function of nucleoplasmin and the implicit relationship with SNBP
diversity The amphibians represent an unique opportunity to address this issue as they contain
genera with SNBPs representative of each of the three main types: Rana (H type); Xenopus (PL type)
and Bufo (P type).
Results: In this work, the presence of nucleoplasmin in oocyte extracts from these three
organisms has been assessed using Western Blotting. We have used mass spectrometry and cloning
techniques to characterize the full-length cDNA sequences of Rana catesbeiana and Bufo marinus
nucleoplasmin. Northern dot blot analysis shows that nucleoplasmin is mainly transcribed in the
egg of the former species. Phylogenetic analysis of nucleoplasmin family members from various
metazoans suggests that amphibian nucleoplasmins group closely with mammalian NPM2 proteins.
Conclusion: We have shown that these organisms, in striking contrast to their SNBPs, all contain
nucleoplasmins with very similar primary structures. This result has important implications as it
suggests that nucleoplasmin's role in chromatin assembly during early zygote development could
have been complemented by the acquisition of a new function of non-specifically removing SNBPs
in sperm chromatin remodeling. This acquired function would have been strongly determined by
the constraints imposed by the appearance and differentiation of SNBPs in the sperm.
Description
BioMed Central
Keywords
Citation
Frehlick et al. The characterization of amphibian nucleoplasmins yields new insight into their role in sperm chromatin remodeling. BMC Genomics 2006, 7 :99