HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) All Versions of this Article: 75/5/741    most recent biolreprod.106.055178v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal My Folders Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Shaman, J. A. Articles by Ward, W. S. Search for Related Content PubMed PubMed Citation Articles by Shaman, J. A. Articles by Ward, W. S. Agricola Articles by Shaman, J. A. Articles by Ward, W. S.

Topoisomerase IIB and an Extracellular Nuclease Interact to Digest Sperm DNA in an Apoptotic-Like Manner¹

Institute for Biogenesis Research, John A. Burns School of Medicine, University of Hawaii, Honolulu, Hawaii 96822

ABSTRACT

We previously demonstrated that mammalian spermatozoa contain a nuclease activity that cleaves DNA into loop-sized fragments. We show here that this activity is mediated by a nuclear matrix-associated topoisomerase IIB (TOP2B) interacting with an extracellular Mn²⁺/Ca²⁺-dependent nuclease. Together, these enzymes cleave all of the DNA into fragments of 50 kb, and this cleavage can be reversed by EDTA. If dithiothreitol is included, the nuclease digests the DNA, and if the protamines are removed the DNA is completely digested. A similar, TOP2B-mediated, chromatin fragmentation, which is reversible, followed by digestion of the DNA by an intracellular nuclease occurs in somatic cells during apoptosis. The extracellular location of the sperm nuclease made it possible to reconstitute the fragmentation activity in isolated spermatozoa, thus allowing us to identify two novel aspects of the mechanism. First, the fragmentation of all of the DNA to 50 kb by TOP2B required the addition of the extracellular nuclease or factor. Second, the subsequent, complete digestion of the DNA by the nuclease could be inhibited by etoposide, suggesting that the nuclease digestion requires TOP2B religation of the cleaved DNA. These data are the first demonstration of an active TOP2B in spermatozoa, suggesting this inert chromatin may be more active than previously thought. They also show that the unique chromatin structure of spermatozoa may provide an important model to study the regulated degradation of chromatin by TOP2B and associated nucleases.

apoptosis, epididymis, gamete biology, sperm, testis

² Correspondence: FAX: 808 956 7316; wward{at}hawaii.edu

¹ Supported by NIH grant HD28501 to W.S.W. and by the Victoria S. and Bradley L. Geist Foundation.

This article has been cited by other articles:

				C Ortega Ferrusola, L Gonzalez Fernandez, J M Morrell, C Salazar Sandoval, B Macias Garcia, H Rodriguez-Martinez, J A Tapia, and F J Pena Lipid peroxidation, assessed with BODIPY-C11, increases after cryopreservation of stallion spermatozoa, is stallion-dependent and is related to apoptotic-like changes Reproduction, July 1, 2009; 138(1): 55 - 63. [Abstract] [Full Text] [PDF]

				C. Spadafora Sperm-mediated 'reverse' gene transfer: a role of reverse transcriptase in the generation of new genetic information Hum. Reprod., April 1, 2008; 23(4): 735 - 740. [Abstract] [Full Text] [PDF]

				H. Kusakabe, R. Yanagimachi, and Y. Kamiguchi Mouse and human spermatozoa can be freeze-dried without damaging their chromosomes Hum. Reprod., February 1, 2008; 23(2): 233 - 239. [Abstract] [Full Text] [PDF]

				F. Leduc, V. Maquennehan, G. B. Nkoma, and G. Boissonneault DNA Damage Response During Chromatin Remodeling in Elongating Spermatids of Mice Biol Reprod, February 1, 2008; 78(2): 324 - 332. [Abstract] [Full Text] [PDF]

				M. Perez-Crespo, P. Moreira, B. Pintado, and A. Gutierrez-Adan Factors From Damaged Sperm Affect Its DNA Integrity and Its Ability to Promote Embryo Implantation in Mice J Androl, January 1, 2008; 29(1): 47 - 54. [Abstract] [Full Text] [PDF]

				Y. Yamauchi, B. Doe, A. Ajduk, and M. A Ward Genomic DNA Damage in Mouse Transgenesis Biol Reprod, November 1, 2007; 77(5): 803 - 812. [Abstract] [Full Text] [PDF]

				Y. Yamauchi, A. Ajduk, J. M Riel, and M. A Ward Ejaculated and Epididymal Mouse Spermatozoa Are Different in Their Susceptibility to Nuclease-Dependent DNA Damage and in Their Nuclease Activity Biol Reprod, October 1, 2007; 77(4): 636 - 647. [Abstract] [Full Text] [PDF]

				Y. Yamauchi, J. A Shaman, S. M Boaz, and W. S. Ward Paternal Pronuclear DNA Degradation Is Functionally Linked to DNA Replication in Mouse Oocytes Biol Reprod, September 1, 2007; 77(3): 407 - 415. [Abstract] [Full Text] [PDF]

				I. Har-Vardi, R. Mali, M. Breietman, Y. Sonin, S. Albotiano, E. Levitas, G. Potashnik, and E. Priel DNA topoisomerases I and II in human mature sperm cells: characterization and unique properties Hum. Reprod., August 1, 2007; 22(8): 2183 - 2189. [Abstract] [Full Text] [PDF]

				R. P. Martins and S. A. Krawetz Decondensing the protamine domain for transcription PNAS, May 15, 2007; 104(20): 8340 - 8345. [Abstract] [Full Text] [PDF]

				D. T. Carrell, B. R. Emery, and S. Hammoud Altered protamine expression and diminished spermatogenesis: what is the link? Hum. Reprod. Update, May 1, 2007; 13(3): 313 - 327. [Abstract] [Full Text] [PDF]

				Y. Yamauchi, J. A. Shaman, and W. S. Ward Topoisomerase II-Mediated Breaks in Spermatozoa Cause the Specific Degradation of Paternal DNA in Fertilized Oocytes Biol Reprod, April 1, 2007; 76(4): 666 - 672. [Abstract] [Full Text] [PDF]