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Brucella is a genus of Gram-negative intracellular pathogens that cause animal and human diseases. Brucella survival and replication inside immune cells is critical for the establishment of chronic infections. Protein modifications by small ubiquitin-related modifier proteins and the NF-κB pathway are involved in many cellular activities, playing major roles in regulating protein function that is essential for pathogenic bacteria during infection. However, the relationship between them in the intracellular survival of Brucella is still largely unknown. We demonstrated that Brucella abortus 2308 infection can activate the expression of small ubiquitin-related modifier-2 proteins in a time-dependent manner. We found the production of Th1 cytokines (IFN-γ and TNF-α) and the transcription of NF-κB/p65 were promoted by overexpression and inhibited by interference of small ubiquitin-related modifier-2. In addition, we showed that small ubiquitin-related modifier-2 can inhibit intracellular survival of Brucella abortus 2308 by regulating activation of the NF-κB pathway. Taken together, this work shows that small ubiquitin-related modifier-2 modification of NF-κB2/p65 is essential for the survival of Brucella abortus 2308 inside macrophages. This work may help to unravel the pathogenic mechanisms of Brucella infections. [ABSTRACT FROM AUTHOR]

To date, a variety of Brucella effector proteins have been found to mediate host cell secretion, autophagy, inflammation, and other signal pathways, but nuclear effector proteins have not yet been reported. We identified the first Brucella nucleomodulin, BspJ, and we screened out the BspJ interaction host proteins NME/NM23 nucleoside diphosphate kinase 2 (NME2) and creatine kinase B (CKB) through yeast two-hybrid and co-immunoprecipitation assays. These proteins are related to the host cell energy synthesis, metabolism, and apoptosis pathways. Brucella nucleomodulin BspJ will decrease the expression level of NME2 and CKB. In addition, BspJ gene deletion strains promoted the apoptosis of macrophages and reduced the intracellular survival of Brucella in host cells. In short, we found nucleomodulin BspJ may directly or indirectly regulate host cell apoptosis through the interaction with NME2 and CKB by mediating energy metabolism pathways in response to the intracellular circulation of Brucella infection, but the mechanism needs further study. [ABSTRACT FROM AUTHOR]

The secretory proteins of Brucella mediate the expression of the bacterium in the host, thereby facilitating intracellular parasitism. With the exception of the recently reported BspJ, the Brucella nucleomodulin has not yet been characterized. We defined the Brucella nucleomodulin BspG and verified six proteins (PCBP1, KMT5C, NDUFS6, PCNA, CIAO2B, and SDHB) that interacted with BspG using a yeast two-hybrid assay and co-immunoprecipitation (CO-IP) screening. The deletion of BspG decreased the intracellular proliferation of B. abortus in both in vivo and in vitro experiments. The analysis found that these interacting proteins were related to energy generation, gene expression, and apoptosis of host cells. The crosstalk between B. abortus nucleomodulin BspG and host DNA replication/mitochondrial respiratory pathways promotes anti-apoptosis and infection, but the mechanism needs additional study. • Defined nucleomodulin BspG for the first time. • Six proteins involved in the host DNA replication process/mitochondrial respiratory pathway interact with BspG. • BspG as a virulence factor promotes host cell anti-apoptosis. [ABSTRACT FROM AUTHOR]