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Poly(ADP-Ribose) Polymerases PARP1 and PARP2 Modulate Topoisomerase II Beta (TOP2B) Function During Chromatin Condensation in Mouse Spermiogenesis

Lookup NU author(s): Professor Caroline AustinORCiD


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To achieve the specialized nuclear structure in sperm necessary for fertilization, dramatic chromatin reorganization steps in developing spermatids are required where histones are largely replaced first by transition proteins and then by protamines. This entails the transient formation of DNA strand breaks to allow for, first, DNA relaxation and then chromatin compaction. However, the nature and origin of these breaks are not well understood. We previously reported that these DNA strand breaks trigger the activation of poly(ADP-ribose) (PAR) polymerases PARP1 and PARP2 and that interference with PARP activation causes poor chromatin integrity with abnormal retention of histones in mature sperm and impaired embryonic survival. Here we show that the activity of topoisomerase II beta (TOP2B), an enzyme involved in DNA strand break formation in elongating spermatids, is strongly inhibited by the activity of PARP1 and PARP2 in vitro, and this is in turn counteracted by the PAR-degrading activity of PAR glycohydrolase. Moreover, genetic and pharmacological PARP inhibition both lead to increased TOP2B activity in murine spermatids in vivo as measured by covalent binding of TOP2B to the DNA. In summary, the available data suggest a functional relationship between the DNA strand break-generating activity of TOP2B and the DNA strand break-dependent activation of PARP enzymes that in turn inhibit TOP2B. Because PARP activity also facilitates histone H1 linker removal and local chromatin decondensation, cycles of PAR formation and degradation may be necessary to coordinate TOP2B-dependent DNA relaxation with histone-to-protamine exchange necessary for spermatid chromatin remodeling.

Publication metadata

Author(s): Meyer-Ficca ML, Lonchar JD, Ihara M, Meistrich ML, Austin CA, Meyer RG

Publication type: Article

Publication status: Published

Journal: Biology of Reproduction

Year: 2011

Volume: 84

Issue: 5

Pages: 900-909

Print publication date: 12/01/2011

ISSN (print): 0006-3363

ISSN (electronic): 1529-7268

Publisher: Society for the Study of Reproduction


DOI: 10.1095/biolreprod.110.090035


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Funder referenceFunder name
Comparative Oncology at University of Pennsylvania
NIH R01 HD48837National Institutes of Health
P30-ES013508Environmental Health Sciences Core Center