Expression and Genetic Analysis of XIAP-Associated Factor 1 (XAF1) in Cancer Cell Lines

• Published in: Genomics (San Diego, Calif.) Vol. 70; no. 1; pp. 113 - 122
• Main Authors: Fong, Wai Gin, Liston, Peter, Rajcan-Separovic, Evica, St. Jean, Martine, Craig, Constance, Korneluk, Robert G.
• Format: Journal Article
• Language: English
• Published: San Diego, CA Elsevier Inc 15.11.2000; Elsevier
• Subjects: Alternative Splicing; Apoptosis; Biological and medical sciences; Biomarkers, Tumor; Cell physiology; Cell transformation and carcinogenesis. Action of oncogenes and antioncogenes; Chromosome Mapping; Female; Fundamental and applied biological sciences. Psychology; Gene Deletion; Gene Duplication; Genomic Library; Humans; In Situ Hybridization, Fluorescence; Intracellular Signaling Peptides and Proteins; Loss of Heterozygosity; Male; Molecular and cellular biology; Neoplasm Proteins - genetics; Neoplasm Proteins - metabolism; p53 gene; Placenta; Pregnancy; Protein Binding; Proteins - metabolism; TP53 gene; Tumor Cells, Cultured; Two-Hybrid System Techniques; X-Linked Inhibitor of Apoptosis Protein; XAF1 gene; XIAP-associated factor 1; Genetic mapping; Human; Cell line; Nucleotide sequence; Chromosome E17; Gene organization; Inhibitor; Gene expression; Carcinogenesis; Physical map; Tumor cell; Apoptosis
• ISSN: 0888-7543; 1089-8646
• DOI: 10.1006/geno.2000.6364

X-linked inhibitor of apoptosis protein (XIAP) is a potent modulator of programmed cell death. XIAP specifically binds and inhibits the function of caspase-3, -7, and -9, key effector proteases of apoptosis. We recently isolated, by yeast two-hybrid screening, a novel 34-kDa zinc finger protein, XIAP-associated factor 1 (XAF1). Both the caspase inhibiting and the anti-apoptotic abilities of XIAP were found to be blocked by overexpressed XAF1. Here, we report the isolation and characterization of the human XAF1 gene. The xaf1 gene consists of seven exons spanning 18 kb. Fluorescence in situ hybridization analysis localized the xaf1 locus at 17p13.2, telomeric to the p53 gene. The xaf1 locus was further refined to YAC 746C10, approximately 3 cM distal to TP53. Microsatellite analysis of the xaf1 locus using the NCI 60 cell line panel revealed significantly decreased heterozygosity at all three polymorphic markers tested, suggesting that allelic loss of the xaf1 gene is prevalent in cancer cell lines. Examination of the same NCI cell line panel for xaf1 RNA expression demonstrated that cancer cell lines exhibited very low levels of mRNA relative to normal human liver. In contrast, XIAP mRNA levels were relatively high in the majority of cancer cell lines tested. We propose that a high level of XIAP to XAF1 expression in cancer cells may provide a survival advantage through the relative increase of XIAP anti-apoptotic function.