Background: FUS has been implicated in the DNA damage response; however, the mechanisms are unknown. Results: FUS recruitment to DNA lesions is PARP-dependent. Depletion of FUS disrupts DNA repair. Conclusion: FUS functions downstream of PARP and promotes double-strand break repair. Significance: This work identifies FUS as a novel factor at DNA lesions and furthers our understanding of RNA-binding proteins in maintaining genomic stability.

Natural killer T (NKT) cells are innate-likeT cells that recognize specific microbial antigens and also display autoreactivity to self-antigens. The nature of NKT-cell autoreactive activation remains poorly understood. We show here that the mitogenactivated protein kinase (MAPK) pathway is operative during human NKT-cell autoreactive activation, but calcium signaling is severely impaired. This results in a response that is biased toward granulocyte macrophage colony-stimulating factor (GM-CSF) secretion because this cytokine requires extracellular signalregulated kinase (ERK) signaling but is not highly calcium dependent, whereas interferon-␥ (IFN-␥), interleukin (IL)-4, and IL-2 production are minimal. Autoreactive activation was associated with reduced migration velocity but did not induce arrest; thus, NKT cells retained the ability to survey antigen presenting cells (APCs). IL-12 and IL-18 stimulated autoreactively activated NKT cells to secrete IFN-␥, and this was mediated by Janus kinase-signal transducers and activators of transcription (JAK-STAT)-dependent signaling without induction of calcium flux. This pathway did not require concurrent contact with CD1d ؉ APCs but was strictly dependent on preceding autoreactive stimulation that induced ERK activation. In contrast, NKT-cell responses to the glycolipid antigen ␣-galactosyl ceramide (␣-GalCer) were dampened by prior autoreactive activation. These results show that NKT-cell autoreactivity induces restricted cytokine secretion and leads to altered basal activation that potentiates innate responsiveness to costimulatory cytokines while modulating sensitivity to foreign antigens. (Blood. 2008;112: 4128-4138) IntroductionNatural killer T (NKT) cells are a subset of regulatory T cells that recognizes lipid antigens presented by CD1d molecules. 1,2 Like innate lymphocytes, NKT cells are among the first responders during microbial infections, and their responses are not necessarily dependent on recognition of foreign antigens. 3 NKT cells have attracted attention because they secrete large amounts of both Th1 and Th2 cytokines rapidly on stimulation and demonstrate a potent ability to modulate immune function. 1,2,4 Remarkably, in some disease models, NKT cells promote proinflammatory immune responses, whereas in others they have a tolerogenic effect. 5 It is not clear what confers the innate-like features of NKT cells or how they mediate contrasting immunologic outcomes in different contexts.Most NKT cells can be activated to secrete cytokines by exposure to CD1d ϩ antigen-presenting cells (APCs) in the absence of microbial antigens, and this appears to depend on presentation of cellular antigens by CD1d. 6-9 NKT cells from germ-free mice and from human cord blood display a phenotype indicating prior activation, [10][11][12] suggesting that NKT cells are autoreactive to self-antigens in vivo. NKT cells have been shown to recognize certain mammalian lipids as antigens presented by CD1d 9,13 ; however, the specific self-antigens responsible for NKT cell autorea...

Weak TCR stimulation of iNKT cells, such as that resulting from self-antigen recognition, induces histone modifications at the IFNG locus that allow the iNKT cells to subsequently produce IFN-γ in response to proinflammatory cytokines alone.

, indicating these molecules likely interact under physiological conditions. Immunofluorescence microscopy confirmed a dual localization of CRHSP-28 and annexin VI, which appeared in a punctate pattern in the supranuclear and apical cytoplasm of acini. Stimulation of cells for 5 min with the secretagogue cholecystokinin enhanced the colocalization of CRHSP-28 and annexin VI within regions of acini immediately below the apical plasma membrane. Tissue fractionation revealed that CRHSP-28 is a peripheral membrane protein that is highly enriched in smooth microsomal fractions of pancreas. Further, the content of CRHSP-28 in microsomes was significantly reduced in pancreatic tissue obtained from rats that had been infused with a secretory dose of cholecystokinin for 40 min, demonstrating that secretagogue stimulation transiently alters the association of CRHSP-28 with membranes in cells. Collectively, the Ca 2؉ -dependent binding of CRHSP-28 and annexin VI, together with their colocalization in the apical cytoplasm, is consistent with a role for these molecules in acinar cell membrane trafficking events that are essential for digestive enzyme secretion.