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Adenovirus inundates the productively infected cell with linear, double-stranded DNA and an abundance of single-stranded DNA. The cellular response to this stimulus is antagonized by the adenoviral E1B and E4 early genes. A mutant group C adenovirus that fails to express the E1B-55K and E4orf3 genes is unable to suppress the DNA-damage response. Cells infected with this double-mutant virus display significant morphological heterogeneity at late times of infection and frequently contain fragmented nuclei. Nuclear fragmentation was due to the translocation of apoptosis inducing factor (AIF) from the mitochondria into the nucleus. The release of AIF was dependent on active poly(ADP-ribose) polymerase-1 (PARP-1), which appeared to be activated by viral DNA replication. Nuclear fragmentation did not occur in AIF-deficient cells or in cells treated with a PARP-1 inhibitor. The E1B-55K or E4orf3 proteins independently prevented nuclear fragmentation subsequent to PARP-1 activation, possibly by altering the intracellular distribution of PAR-modified proteins., (Copyright © 2014 Elsevier Inc. All rights reserved.)

To investigate the intrinsic activities of the epidermal growth factor receptor and the role of its kinase domain in these functions within a cellular environment lacking endogenous ErbB protein expression, wild-type EGF receptor (WT-EGFR) and two kinase-impaired mutants, D813A and K721R, were expressed in 32D murine hematopoietic cells, a line which is normally dependent on interleukin 3 (IL3) for growth and survival. Addition of EGF in the absence of IL3 stimulates receptor autophosphorylation and, in the presence of serum, mitosis in cells expressing WT-EGFR, but not in cells expressing D813A or K721R. Unexpectedly, cells expressing WT-EGFR or K721R exhibited IL3-independent survival in the presence of fetal bovine serum; parental 32D cells and cells expressing D813A did not survive, apparently undergoing apoptosis in the absence of IL3, whether or not serum was present. Addition of EGF did not prevent the apoptosis of WT-EGFR or K721R cells in serum-free medium. Activation of Akt was not necessary to mediate the prosurvival activity of EGF receptor expression. These results suggest that the EGF receptor can mediate the prevention of apoptosis independently of both receptor-ligand binding and receptor kinase activity, and this activity is disrupted by the D813A mutation.