Disease relevance of Dffa

• A caspase-activated deoxyribonuclease (CAD) and its inhibitor (ICAD) have now been identified in the cytoplasmic fraction of mouse lymphoma cells [1].
• Presence of DNA fragmentation and lack of neuroprotective effect in DFF45 knockout mice subjected to traumatic brain injury [2].
• Our results suggest that a lack of DFF45 can lead to neuronal resistance to excessive activity-induced toxicity [3].
• This was achieved with the use of MCF-7 cells, a caspase-3-deficient breast adenocarcinoma cell line, thymocytes isolated from DFF45 (the inhibitory and chaperone subunit of the DNA fragmentation factor subunit, DFF40) deficient mice, and HeLa cells, a DNAS1L3-deficient cervical carcinoma cell line [4].

High impact information on Dffa

• We show here that Cidea, a protein of unknown function sharing sequence similarity with the N-terminal region of DNA fragmentation factors Dffb and Dffa, is expressed at high levels in BAT [5].
• However, although transgenic mice lacking DFF45 or its caspase cleavage site have significantly reduced DNA fragmentation, these mice still show residual DNA fragmentation and are phenotypically normal [6].
• A caspase-activated DNase that degrades DNA during apoptosis, and its inhibitor ICAD [1].
• When human Jurkat cells were transformed with ICAD-expressing plasmid, occupation of the receptor Fas, which normally triggers apoptosis, did not result in DNA degradation [7].
• These results not only indicate that loss of an SR protein splicing factor can induce cell cycle arrest and apoptosis, but also illustrate the important role of ICAD and its regulation by alternative splicing in the process of apoptotic DNA fragmentation [8].

Biological context of Dffa

• Here, we describe the assignment of murine CAD and ICAD genes to the distal part of murine chromosome 4 [9].
• Molecular cloning and structural analysis indicated that CAD and ICAD genes are comprised of 7 and 6 exons, respectively [9].
• An expression plasmid containing mouse ICAD-L mutated at the caspase-3-recognition sites was then introduced into Jurkat and TF-1 cells [10].
• There is sequence homology of about 80 amino acid residues at the N termini of CAD and ICAD (called the CAD domain) [11].
• ICAD did not protect CAD from the chemical modification of the histidine residues, indicating that it does not mask the active site of CAD [12].

Anatomical context of Dffa

• CAD was predominantly associated with ICAD-L in these cell lines [13].
• In contrast, reticulocyte lysates stimulated ICAD-L- and ATP-dependent renaturation of denatured CAD without requiring a high concentration of reducing agents [14].
• Among eight different caspases examined, recombinant caspases 3 and 7 specifically cleaved ICAD synthesized in a cell-free system [10].
• We also show expression of a caspase cleavage-resistant form of ICAD (ICAD-DM) in Jurkat and HeLa cells abolished DNA fragmentation and also dramatically reduced histone release in apoptotic cells [15].
• We showed that CAD and ICAD are co-localized in microsome, nuclei and cytosol in unstimulated thymocytes [16].

Associations of Dffa with chemical compounds

• Moreover, DFF45-deficient thymocytes are resistant to DNA fragmentation with in vivo dexamethasone treatment [17].
• DFF45(-/-) and DFF45(+/+) cells were equally sensitive to the DNA-damaging agent and PARP activator N-methyl-N'-nitro-N-nitrosoguanidine [18].
• Our results indicate that phosphocreatine protects ICAD/DFF45-like protein from proteolysis, probably through kinase actions, resulting in its resistance to caspase cleavage and leading to an inhibition of DNA fragmentation [19].
• In contrast, most ICAD transfected ACHN cell tumors continued to grow after cisplatin treatment [20].
• MATERIALS AND METHODS: The liposome mediated gene transfer method was used to introduce ICAD complementary DNA into ACHN cells and the expression of ICAD protein per clone was evaluated by Western blot analysis [20].

Physical interactions of Dffa

• In proliferating cells, CAD is complexed with ICAD (inhibitor of CAD) and its DNase activity is suppressed [12].

Enzymatic interactions of Dffa

• DFF45 is a subunit of the DNA fragmentation factor (DFF) that is cleaved by caspase-3 during apoptosis [21].

Regulatory relationships of Dffa

• Following in vivo TCR engagement, ICAD located in cytosol and microsome was degraded and the resulting activated CAD induced chromosomal DNA fragmentation [16].
• (+)-Catechin partially inhibited the activation of caspase-3, thereby both cleavage of poly (ADP-ribose) polymerase (PARP) and degradation of inhibitor of caspase-activated DNase (ICAD) were effectively abolished [22].
• Cytosolic nuclease activated by caspase-3 and inhibited by DFF-45 [23].

Other interactions of Dffa

• DFF45/ICAD can be directly processed by granzyme B during the induction of apoptosis [24].
• CD95/Fas-mediated apoptosis was enhanced by CIDEs but inhibited by DFF45 [21].
• Here we report the identification and characterization of two mammalian genes, CIDE-A and CIDE-B, encoding highly related proteins with homology to the N-terminal region of DFF45 [21].
• The activation of caspase-3 and mitochondrial events important in apoptotic signaling, including the loss of mitochondrial membrane potential and the release of cytochrome c, induced by TNF were similarly delayed in DFF45(-/-) fibroblasts [18].
• Caspases were activated, and the death substrates of caspases, lamin B and ICAD (an inhibitor of caspase-activated DNase), were cleaved in this cell death process [25].

Analytical, diagnostic and therapeutic context of Dffa

• We identified two caspase-3 cleavage sites in ICAD by site-directed mutagenesis [7].
• When purified recombinant ICAD protein was separated by gel chromatography, the molecular weight of ICAD was detected at approximately 440 and 45 K [26].

References