Function of RAD6B and RNF8 in spermatogenesis

Abstract

Histone ubiquitination regulates sperm formation and is important for nucleosome removal during spermatogenesis. RNF8 is an E3 ubiquitin ligase, and RAD6B is an E2 ubiquitin-conjugating enzyme. Both proteins participate in DNA damage repair processes via histone ubiquitination. Loss of RNF8 or RAD6B can lead to sterility in male mice. However, the specific mechanisms regulating these ubiquitin-mediated processes are unclear. In this study, we found that RNF8 knockout mice were either subfertile or sterile based on the numbers of offspring they produced. We explored the mechanism by which RAD6B and RNF8 knockouts cause infertility in male mice and compared the effects of their loss on spermatogenesis. Our results demonstrate that RAD6B can polyubiquitinate histones H2 A and H2B. In addition, RNF8 was shown to monoubiquitinate histones H2 A and H2B. Furthermore, we observed that absence of histone ubiquitination was not the only reason for infertility. Senescence played a role in intensifying male sterility by affecting the number of germ cells during spermatogenesis. In summary, both histone ubiquitination and senescence play important roles in spermatogenesis.

RNF8 is not required for histone-to-protamine exchange in spermiogenesis

“…On the other hand, Rnf8-KO mice in our colony did not show abrogation of spermiogenic progression in Rnf8-KO testes, enabling us to confirm that RNF8 is not required for histone-to-protamine exchange. Curiously, the same Rnf8-KO mice were reported to be subfertile in another study (Guo et al, 2018). While that study claimed that RNF8 is required for histone-protamine exchange, fertile Rnf8-KO sperm must have underwent normal histone-protamine exchange to enable fertilization, supporting our conclusion that RNF8 is not required for the histone-to-protamine exchange.…”

“…This same line of Rnf8-KO mice was widely used in previous studies of the function of RNF8 in spermatogenesis (Adams et al, 2018;Guo et al, 2018;Hasegawa et al, 2015;Ichijima et al, 2011;Lu et al, 2010;Lu et al, 2013;Santos et al, 2010;Sin et al, 2012;Sin et al, 2015), including the initial study by Lu et al (2010) which suggested a requirement for RNF8 in mediating histone-to-protamine exchange.…”

“…Variable abnormal gene expression of sex chromosome-linked genes in Rnf8-KO testes could modulate phenotypic outcomes (i.e. spermiogenic progression) in distinct genetic backgrounds or environments among different studies (Guo et al, 2018;Lu et al, 2010;Sin et al, 2012). Additionally, a chromatin-remodeling nuclear protein, CHD5 has been reported as another factor that controls hyperacetylation of H4 at K5/8/16, histone-to-protamine exchange and chromatin condensation in sperm heads (Li et al, 2014;Zhuang et al, 2014), which shows substantial similarity with the Rnf8-KO phenotype reported by Lu et al (2010).…”

“…It is made The copyright holder for this preprint this version posted December 6, 2020. ; https://doi.org/10.1101/2020.12.05.413005 doi: bioRxiv preprint 4 (2017) concluded that MIWI has a piRNA-independent function, but instead has a RNF8-dependent function in histone-to-protamine exchange. Further, an additional study suggested that RNF8 is required for histone-to-protamine exchange based on the presence of testis-specific histone H2B in sperm nuclei of Rnf8-deficient mice (Guo et al, 2018). These studies have spawned a lingering view in the field that RNF8 is required for histone-to-protamine exchange (Wang et al, 2019;Yan, 2017).…”

Role of HP1β during spermatogenesis and DNA replication

“…During the germ cell reproductive process, epigenetic chromatin modifications such as methylation, acetylation and ubiquitination play major roles (Gannon et al, 2014). (Guo et al, 2018;Simhadri et al, 2014;Sun et al, 2016;Ward et al, 2003).…”