PU.1 opposes IL-7-dependent proliferation of developing B cells with involvement of the direct target gene bruton tyrosine kinase.

Deletion of genes encoding the E26 transformation-specific transcription factors PU.1 and Spi-B in B cells (CD19-CreΔPB mice) leads to impaired B cell development, followed by B cell acute lymphoblastic leukemia at 100% incidence and with a median survival of 21 wk. However, little is known about the target genes that explain leukemogenesis in these mice. In this study we found that immature B cells were altered in frequency in the bone marrow of preleukemic CD19-CreΔPB mice. Enriched pro-B cells from CD19-CreΔPB mice induced disease upon transplantation, suggesting that these were leukemia-initiating cells. Bone marrow cells from preleukemic CD19-CreΔPB mice had increased responsiveness to IL-7 and could proliferate indefinitely in response to this cytokine. Bruton tyrosine kinase (BTK), a negative regulator of IL-7 signaling, was reduced in preleukemic and leukemic CD19-CreΔPB cells compared with controls. Induction of PU.1 expression in cultured CD19-CreΔPB pro-B cell lines induced Btk expression, followed by reduced STAT5 phosphorylation and early apoptosis. PU.1 and Spi-B regulated Btk directly as shown by chromatin immunoprecipitation analysis. Ectopic expression of BTK was sufficient to induce apoptosis in cultured pro-B cells. In summary, these results suggest that PU.1 and Spi-B activate Btk to oppose IL-7 responsiveness in developing B cells.

Nigella sativa and its active constituent thymoquinone in oral health.

In this review, we summarized published reports that investigated the role of Nigella sativa (NS) and its active constituent, thymoquinone (TQ) in oral health and disease management. The literature studies were preliminary and scanty, but the results revealed that black seed plants have a potential therapeutic effect for oral and dental diseases. Such results are encouraging for the incorporation of these plants in dental therapeutics and hygiene products. However, further detailed preclinical and clinical studies at the cellular and molecular levels are required to investigate the mechanisms of action of NS and its constituents, particularly TQ.

The transcription factor PU.1 is a critical regulator of cellular communication in the immune system.

PU.1 is an E26 transformation-specific family transcription factor that is required for development of the immune system. PU.1 functions at both early and late stages of lymphoid and myeloid differentiation. At least 110 direct target genes of PU.1 have been identified since its discovery in 1988. We used the published literature to determine if aspects of PU.1 function can be inferred from the identity of target genes that are directly activated. This analysis revealed that 61% of described PU.1 target genes encode extracellular proteins or transmembrane proteins, most of which are involved in cellular communication. The genes activated by PU.1 can be grouped into pathways based on function. Specific examples of cellular communication pathways regulated by PU.1 include (1) antibodies and antibody receptors, (2) cytokines and cytokine receptors regulating leukocyte growth and development, and (3) cytokines and cytokine receptors regulating inflammation. As a consequence of mutation or repression of the gene encoding PU.1, hematopoietic progenitors may be generated but there is a "failure to thrive" because they cannot interact with their environment. The loss of cellular communication caused by reduced PU.1 levels can lead to leukemia. In summary, PU.1 is a critical regulator of cellular communication in the immune system.