p65/RelA binds and activates the beclin 1 promoter

We unveiled novel p65/RelA consensus sites in the promoter of the beclin 1 gene and demonstrate that p65/RelA positively modulates canonical autophagy in various human cell lines both under basal conditions and upon induction by ceramide. Interestingly, we find that T cell receptor-dependent activation of Jurkat cells triggers an increase in the binding of p65/RelA to the beclin 1 promoter accompanied by enhanced autophagy, suggesting that p65/RelA could regulate T-cell activation and homeostasis through autophagy.     

RelA/p65 functions to maintain cellular senescence by regulating genomic stability and DNA repair

Nuclear factor (NF)-κB is a positive regulator of tumour development and progression, but how it functions in normal cells leading to oncogenesis is not clear. As cellular senescence has proven to be an intrinsic tumour suppressor mechanism that cells must overcome to establish deregulated growth, we used primary fibroblasts to follow NF-κB function in cells transitioning from senescence to subsequent immortalization. Our findings show that RelA/p65^−/− murine fibroblasts immortalize at considerably faster rates than RelA/p65^+/+ cells. The ability of RelA/p65^−/− fibroblasts to escape senescence earlier is due to their genomic instability, characterized by high frequencies of DNA mutations, gene deletions and gross chromosomal translocations. This increase in genomic instability is closely related to a compromised DNA repair that occurs in both murine RelA/p65^−/− fibroblasts and tissues. Significantly, these results can also be duplicated in human fibroblasts lacking NF-κB. Altogether, our findings present a fresh perspective on the role of NF-κB as a tumour suppressor, which acts in pre-neoplastic cells to maintain cellular senescence by promoting DNA repair and genomic stability.     

Subcellular localization of the human proto-oncogene protein DEK

Recent data revealed that DEK associates with splicing complexes through interactions mediated by serine/arginine-repeat proteins. However, the DEK protein has also been shown to change the topology of DNA in chromatin in vitro. This could indicate that the DEK protein resides on cellular chromatin. To investigate the in vivo localization of DEK, we performed cell fractionation studies, immunolabeling, and micrococcal nuclease digestion analysis. Most of the DEK protein was found to be released by DNase treatment of nuclei, and only a small amount by treatment with RNase. Furthermore, micrococcal nuclease digestion of nuclei followed by glycerol gradient sedimentation revealed that DEK co-sedimentates with oligonucleosomes, clearly demonstrating that DEK is associated with chromatin in vivo. Additional chromatin fractionation studies, based on the different accessibilities to micrococcal nuclease, showed that DEK is associated both with extended, genetically active and more densely organized, inactive chromatin. We found no significant change in the amount and localization of DEK in cells that synchronously traversed the cell cycle. In summary these data demonstrate that the major portion of DEK is associated with chromatin in vivo and suggest that it might play a role in chromatin architecture.