DNA fragmentation factor subunit alpha (DFFA), also known as Inhibitor of caspase-activated DNase (ICAD), is a protein that in humans is encoded by the DFFAgene.
Apoptosis is a cell death process that removes toxic and/or useless cells during mammalian development. The apoptotic process is accompanied by shrinkage and fragmentation of the cells and nuclei and degradation of the chromosomal DNA into nucleosomal units. DNA fragmentation factor (DFF) is a heterodimeric protein of 40-kD (DFFB) and 45-kD (DFFA) subunits. DFFA is the substrate for caspase-3 and triggers DNA fragmentation during apoptosis. DFF becomes activated when DFFA is cleaved by caspase-3. The cleaved fragments of DFFA dissociate from DFFB, the active component of DFF. DFFB has been found to trigger both DNA fragmentation and chromatin condensation during apoptosis. Two alternatively spliced transcript variants encoding distinct isoforms have been found for this gene.
The C-terminaldomain of DFFA (DFF-C) consists of four alpha-helices, which are folded in a helix-packing arrangement, with alpha-2 and alpha-3 packing against a long C-terminal helix (alpha-4). The main function of this domain is the inhibition of DFFB by binding to its C-terminal catalytic domain through ionic interactions, thereby inhibiting the fragmentation of DNA in the apoptotic process. In addition to blocking the DNase activity of DFFB, the C-terminal region of DFFA is also important for the DFFB-specific folding chaperone activity, as demonstrated by the ability of DFFA to refold DFFB.
^Leek JP, Carr IM, Bell SM, Markham AF, Lench NJ (Jun 1998). "Assignment of the DNA fragmentation factor gene (DFFA) to human chromosome bands 1p36.3→p36.2 by in situ hybridization". Cytogenet Cell Genet. 79 (3–4): 212–3. doi:10.1159/000134725. PMID9605855.
^Liu X, Zou H, Slaughter C, Wang X (May 1997). "DFF, a heterodimeric protein that functions downstream of caspase-3 to trigger DNA fragmentation during apoptosis". Cell. 89 (2): 175–84. doi:10.1016/S0092-8674(00)80197-X. PMID9108473.
^Fukushima K, Kikuchi J, Koshiba S, Kigawa T, Kuroda Y, Yokoyama S (August 2002). "Solution structure of the DFF-C domain of DFF45/ICAD. A structural basis for the regulation of apoptotic DNA fragmentation". J. Mol. Biol. 321 (2): 317–27. doi:10.1016/S0022-2836(02)00588-0. PMID12144788.
^Ewing, Rob M; Chu Peter; Elisma Fred; Li Hongyan; Taylor Paul; Climie Shane; McBroom-Cerajewski Linda; Robinson Mark D; O'Connor Liam; Li Michael; Taylor Rod; Dharsee Moyez; Ho Yuen; Heilbut Adrian; Moore Lynda; Zhang Shudong; Ornatsky Olga; Bukhman Yury V; Ethier Martin; Sheng Yinglun; Vasilescu Julian; Abu-Farha Mohamed; Lambert Jean-Philippe; Duewel Henry S; Stewart Ian I; Kuehl Bonnie; Hogue Kelly; Colwill Karen; Gladwish Katharine; Muskat Brenda; Kinach Robert; Adams Sally-Lin; Moran Michael F; Morin Gregg B; Topaloglou Thodoros; Figeys Daniel (2007). "Large-scale mapping of human protein–protein interactions by mass spectrometry". Mol. Syst. Biol. England. 3 (1): 89. doi:10.1038/msb4100134. PMC1847948. PMID17353931.
^McCarty, J S; Toh S Y; Li P (Oct 1999). "Study of DFF45 in its role of chaperone and inhibitor: two independent inhibitory domains of DFF40 nuclease activity". Biochem. Biophys. Res. Commun. UNITED STATES. 264 (1): 176–80. doi:10.1006/bbrc.1999.1497. ISSN0006-291X. PMID10527860.
Nakanuma Y, Tsuneyama K, Sasaki M, Harada K (2000). "Destruction of bile ducts in primary biliary cirrhosis". Baillière's best practice & research. Clinical gastroenterology. 14 (4): 549–70. doi:10.1053/bega.2000.0103. PMID10976014.
Suzuki Y, Yoshitomo-Nakagawa K, Maruyama K, et al. (1997). "Construction and characterization of a full length-enriched and a 5'-end-enriched cDNA library". Gene. 200 (1–2): 149–56. doi:10.1016/S0378-1119(97)00411-3. PMID9373149.
Enari M, Sakahira H, Yokoyama H, et al. (1998). "A caspase-activated DNase that degrades DNA during apoptosis, and its inhibitor ICAD". Nature. 391 (6662): 43–50. doi:10.1038/34112. PMID9422506.
Liu X, Zou H, Widlak P, et al. (1999). "Activation of the apoptotic endonuclease DFF40 (caspase-activated DNase or nuclease). Oligomerization and direct interaction with histone H1". J. Biol. Chem. 274 (20): 13836–40. doi:10.1074/jbc.274.20.13836. PMID10318789.
Gu J, Dong RP, Zhang C, et al. (1999). "Functional interaction of DFF35 and DFF45 with caspase-activated DNA fragmentation nuclease DFF40". J. Biol. Chem. 274 (30): 20759–62. doi:10.1074/jbc.274.30.20759. PMID10409614.
McCarty JS, Toh SY, Li P (1999). "Study of DFF45 in its role of chaperone and inhibitor: two independent inhibitory domains of DFF40 nuclease activity". Biochem. Biophys. Res. Commun. 264 (1): 176–80. doi:10.1006/bbrc.1999.1497. PMID10527860.
McCarty JS, Toh SY, Li P (1999). "Multiple domains of DFF45 bind synergistically to DFF40: roles of caspase cleavage and sequestration of activator domain of DFF40". Biochem. Biophys. Res. Commun. 264 (1): 181–5. doi:10.1006/bbrc.1999.1498. PMID10527861.
Lugovskoy AA, Zhou P, Chou JJ, et al. (2000). "Solution structure of the CIDE-N domain of CIDE-B and a model for CIDE-N/CIDE-N interactions in the DNA fragmentation pathway of apoptosis". Cell. 99 (7): 747–55. doi:10.1016/S0092-8674(00)81672-4. PMID10619428.
Otomo T, Sakahira H, Uegaki K, et al. (2000). "Structure of the heterodimeric complex between CAD domains of CAD and ICAD". Nat. Struct. Biol. 7 (8): 658–62. doi:10.1038/77957. PMID10932250.
Charrier L, Jarry A, Toquet C, et al. (2002). "Growth phase-dependent expression of ICAD-L/DFF45 modulates the pattern of apoptosis in human colonic cancer cells". Cancer Res. 62 (7): 2169–74. PMID11929840.