Highlights d The PIDDosome controls hepatocyte ploidy during postnatal development & regeneration d The PIDDosome defines the speed of liver regeneration posthepatectomy d Aneuploidy in the liver correlates with basal ploidy state but is not limited by CASP2 d E2F family members regulate expression of CASP2 and PIDD1 for liver ploidy control

SummaryIntestinal epithelial cells secrete the chemokine interleukin (IL)-8 in the course of inflammation. Because heat shock proteins (Hsps) and butyrate confer protection to enterocytes, we investigated whether they modulate Salmonella enterica serovar Enteritidis ( S. In a dose-dependent manner, higher butyrate concentrations enhanced IL-8 secretion to maximal levels followed by a gradual but stable decline. This decline was associated with increasing production of Hsp70 and was more vivid in crypt-like cells. In addition, the higher concentrations abolished the heat shock inhibitory effect. Instead, they promoted the IL-8 production in heat-shocked cells even in the absence of S. serovar Enteritidis . We conclude that heat shock and low concentrations of butyrate inhibit IL-8 production by Caco-2 cells exposed to S. serovar Enteritidis . Higher butyrate concentrations stimulate the chemokine production and override the inhibitory effect of the heat shock. The IL-8 down-regulation could in part be mediated via production of Hsp70.

Upregulation of the E2F-dependent transcriptional network has been identified in nearly every human malignancy and is an important driver of tumorigenesis. Two members of the E2F family, E2F7 and E2F8, are potent repressors of E2F-dependent transcription. They are atypical in that they do not bind to dimerization partner (DP) proteins and are not controlled by pRb. The physiological relevance of E2F7 and E2F8 remains incompletely understood, largely because tools to manipulate their activity in vivo have been lacking. Here, we generated transgenic mice with doxycycline-controlled transcriptional activation of E2f7 and E2f8 and induce their expression during postnatal development, in adulthood, and in the context of cancer. Systemic induction of E2f7 and to lesser extendE2f8 transgenes in juvenile mice impaired cell proliferation, caused replication stress, DNA damage and apoptosis, and inhibited animal growth. In adult mice, however, E2F7 and E2F8 induction was well tolerated, yet profoundly interfered with DNA replication, DNA integrity and cell proliferation in DEN-induced liver tumors. Conclusion: Collectively, our findings demonstrate that atypical E2Fs can override cellcycle entry and progression governed by other E2F-family members, and suggest that this property can be exploited to inhibit proliferation of neoplastic hepatocytes when growth and development have subsided during adulthood.

Highlights d Individual cycling cancer cells display enhanced E2F target gene expression d E2F7/8 deletion or E2F3 overexpression overrides cell-cycle exit after DNA damage d Elevated levels of the E2F target Emi1 prevent DNA-damageinduced cell-cycle exit d The cell-cycle exit after DNA damage is transient and leads to endoreplication

E2F transcription factors control the oscillating expression pattern of multiple target genes during the cell cycle. Activator E2Fs, E2F1-3, induce an upswing of E2F targets, which is essential for the G1-to-S phase transition, whereas atypical E2Fs, E2F7 and E2F8, mediate a downswing of the same targets during late S, G2, and M phase. Expression of atypical E2Fs is induced by E2F1-3, but it is unknown how atypical E2Fs are inactivated in a timely manner. Using molecular assays, time lapse microscopy, and flow cytometry we now demonstrate that E2F7 and E2F8 are substrates of the Anaphase Promoting Cyclosome/Complex (APC/C). Removal of CDH1, or mutating the CDH1-interacting KEN boxes, stabilized E2F7/8 from anaphase onwards and during G1. Expressing KEN-mutant E2F7 during G1 severely impairs S-phase entry and eventually results in cell death. Furthermore, we show that E2F8, but not E2F7, interacts also with APC/CCdc20. Importantly, atypical E2Fs can activate the APC/CCdh1 by repressing its inhibitors Emi1, cyclin A, and cyclin E. In conclusion, we uncovered a feedback loop between atypical E2Fs and APC/CCdh1, which ensures balanced expression of cell cycle genes and normal cell cycle progression. Citation Format: Michiel Boekhout, Ruixue Yuan, Annelotte P. Wondergem, Hendrika A. Segeren, Elsbeth A. van Liere, Nesibu Awol, Imke Jansen, Rob MF Wolthuis, Alain de Bruin, Bart Westendorp. Feedback regulation between atypical E2Fs and APC/CCdh1 coordinates cell cycle progression.. [abstract]. In: Proceedings of the AACR Precision Medicine Series: Cancer Cell Cycle - Tumor Progression and Therapeutic Response; Feb 28-Mar 2, 2016; Orlando, FL. Philadelphia (PA): AACR; Mol Cancer Res 2016;14(11_Suppl):Abstract nr B14.