The deubiquitinase cofactor UAF1 interacts with USP1 and plays an essential role in spermiogenesis.

Spermiogenesis defines the final phase of male germ cell differentiation. While multiple deubiquitinating enzymes have been linked to spermiogenesis, the impacts of deubiquitination on spermiogenesis remain poorly characterized. Here, we investigated the function of UAF1 in mouse spermiogenesis. We selectively deleted Uaf1 in premeiotic germ cells using the Stra8-Cre knock-in mouse strain (Uaf1 sKO), and found that Uaf1 is essential for spermiogenesis and male fertility. Further, UAF1 interacts and colocalizes with USP1 in the testes. Conditional knockout of Uaf1 in testes results in disturbed protein levels and localization of USP1, suggesting that UAF1 regulates spermiogenesis through the function of the deubiquitinating enzyme USP1. Using tandem mass tag-based proteomics, we identified that conditional knockout of Uaf1 in the testes results in reduced levels of proteins that are essential for spermiogenesis. Thus, we conclude that the UAF1/USP1 deubiquitinase complex is essential for normal spermiogenesis by regulating the levels of spermiogenesis-related proteins.

ImuA Facilitates SOS Mutagenesis by Inhibiting RecA-Mediated Activity in Myxococcus xanthus.

Bacteria have two pathways to restart stalled replication forks caused by environmental stresses, error-prone translesion DNA synthesis (TLS) catalyzed by TLS polymerase and error-free template switching catalyzed by RecA, and their competition on the arrested fork affects bacterial SOS mutagenesis. DnaE2 is an error-prone TLS polymerase, and its functions require ImuA and ImuB. Here, we investigated the transcription of imuA, imuB, and dnaE2 in UV-C-irradiated Myxococcus xanthus and found that the induction of imuA occurred significantly earlier than that of the other two genes. Mutant analysis showed that unlike that of imuB or dnaE2, the deletion of imuA significantly delayed bacterial regrowth and slightly reduced the bacterial mutation frequency and UV resistance. Transcriptomic analysis revealed that the absence of ImuA released the expression of some known SOS genes, including recA1, recA2, imuB, and dnaE2. Yeast two-hybrid and pulldown analyses proved that ImuA interacts physically with RecA1 besides ImuB. Protein activity analysis indicated that ImuA had no DNA-binding activity but inhibited the DNA-binding and recombinase activity of RecA1. These findings indicate the new role of ImuA in SOS mutagenesis; that is, ImuA inhibits the recombinase activity of RecA1, thereby facilitating SOS mutagenesis in M. xanthus. IMPORTANCE DnaE2 is responsible for bacterial SOS mutagenesis in nearly one-third of sequenced bacterial strains. However, its mechanism, especially the function of one of its accessory proteins, ImuA, is still unclear. Here, we report that M. xanthus ImuA could affect SOS mutagenesis by inhibiting the recombinase activity of RecA1, which helps to explain the mechanism of DnaE2-dependent TLS and the selection of the two restart pathways to repair the stalled replication fork.

NLRP3 inflammasome is involved in nerve recovery after sciatic nerve injury.

The activation of the inflammasome plays an important role in the central nervous system. However, only a few studies have investigated the effects of inflammasome activation in the peripheral nerve, especially in the sciatic nerve, and the mechanism of this activation remains elusive. Moreover, how interleukin-1 beta (IL-1ß) is produced after sciatic nerve injury is also unknown. In our study, we aimed to investigate whether the nucleotide-binding oligomerization domain-like pyrin domain containing protein 3 (NLRP3) inflammasome is activated after sciatic nerve injury and to explore its role in sciatic nerve injury. The results of immunoblotting and immunofluorescence microscopy indicate that the NLRP3 inflammasome was activated after sciatic nerve injury in wild-type (WT) mice, as demonstrated by upregulated inflammasome-related components, e.g., NLRP3, procaspase-1 and ASC. Furthermore, upregulated inflammasome-related components cis-cleavage precursor IL-1ß (proIL-1ß) and precursor interleukin-18 (proIL-18) to IL-1ß and IL-18, contributing to the inflammatory response. Consequently, the inflammatory response after sciatic nerve injury in NLRP3 knockout (NLRP3-KO) mice was less severe than that in WT mice. Moreover, NLRP3-KO mice exhibited an increased sciatic functional index (SFI), which was determined by footprint analysis, suggesting that NLRP3 deficiency is beneficial to sciatic nerve recovery after injury. Therefore, our results indicate that NLRP3 is involved in the recovery from sciatic nerve injury and mediates the production of inflammatory factors, such as IL-1ß, after sciatic nerve injury.