Nature. 2013 Jun 2. doi: 10.1038/nature12199. [Epub ahead of print]
BACH2 represses effector programs to stabilize Treg-mediated immune homeostasis.
Roychoudhuri R, Hirahara K, Mousavi K, Clever D, Klebanoff CA, Bonelli M, Sciumè G, Zare H, Vahedi G, Dema B, Yu Z, Liu H, Takahashi H, Rao M, Muranski P, Crompton JG, Punkosdy G, Bedognetti D, Wang E, Hoffmann V, Rivera J, Marincola FM, Nakamura A, Sartorelli V, Kanno Y, Gattinoni L, Muto A, Igarashi K, O'Shea JJ, Restifo NP.
1] Center for Cancer Research, National Cancer Institute, National Institutes of Health (NIH), Bethesda, Maryland 20892, USA [2].
Through their functional diversification, distinct lineages of CD4+ T cells can act to either drive or constrain immune-mediated pathology. Transcription factors are critical in the generation of cellular diversity, and negative regulators antagonistic to alternate fates often act in conjunction with positive regulators to stabilize lineage commitment. Genetic polymorphisms within a single locus encoding the transcription factor BACH2 are associated with numerous autoimmune and allergic diseases including asthma, Crohn's disease, coeliac disease, vitiligo, multiple sclerosis and type 1 diabetes. Although these associations point to a shared mechanism underlying susceptibility to diverse immune-mediated diseases, a function for BACH2 in the maintenance of immune homeostasis has not been established. Here, by studying mice in which the Bach2 gene is disrupted, we define BACH2 as a broad regulator of immune activation that stabilizes immunoregulatory capacity while repressing the differentiation programs of multiple effector lineages in CD4+ T cells. BACH2 was required for efficient formation of regulatory (Treg) cells and consequently for suppression of lethal inflammation in a manner that was Treg-cell-dependent. Assessment of the genome-wide function of BACH2, however, revealed that it represses genes associated with effector cell differentiation. Consequently, its absence during Treg polarization resulted in inappropriate diversion to effector lineages. In addition, BACH2 constrained full effector differentiation within TH1, TH2 and TH17 cell lineages. These findings identify BACH2 as a key regulator of CD4+ T-cell differentiation that prevents inflammatory disease by controlling the balance between tolerance and immunity.
and, while not related to autoimmunity.....
Leukemia. 2013 Feb;27(2):409-15. doi: 10.1038/leu.2012.220. Epub 2012 Aug 3.
Transcriptional suppression of BACH2 by the Bcr-Abl oncoprotein is mediated by PAX5.
Casolari DA, Makri M, Yoshida C, Muto A, Igarashi K, Melo JV.
Department of Haematology, Centre for Cancer Biology, SA Pathology University of Adelaide, Adelaide, South Australia, Australia.
Bach2 is a lymphoid-specific transcription factor with a prominent role in B-cell development and apoptosis-induction in response to oxidative stress. We previously showed that Bach2 is downregulated in chronic myeloid leukaemia (CML), and here we demonstrate the mechanism by which Bcr-Abl mediates this phenomenon. We have cloned a 3.9?Kb genomic DNA fragment upstream of the transcription initiation site, and delineated the core and proximal BACH2 promoter regions. Transient BCR-ABL expression led to significant reduction in BACH2 promoter activity and this effect was dependent on the kinase function of the oncoprotein. Sequential deletions disclosed several regulatory elements within the promoter region, as well as within BACH2 exonic sequences. Analysis of these elements and transient transfection assays led to the identification of the Pax5 transcription factor as a potent trans-activator of BACH2, whose effect is predominantly mediated through occupation of a binding site on the BACH2 promoter, as demonstrated by both in vitro and in vivo experiments. Overall, our data show that Pax5 functions as an intermediate effector in the Bcr-Abl-mediated transcriptional repression of BACH2. The current results, combined with previous reports, establish Pax5 and Bach2 as transcriptional targets of Bcr-Abl, whose downregulation may contribute to lymphoid blast crisis of CML. |
