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Identification of v-Rel oncogene-induced inhibitor of apoptosis by differential display
1Department of Microbiology and the Institute for Cellular and Molecular Biology, University of Texas at Austin, 78712-1095, USA.
Abstract:
The v-Rel oncoprotein is a member of the Rel/NF-kappaB family of transcription factors. v-Rel induces oncogenic transformation and inhibits apoptosis. To identify aberrantly expressed cellular genes in v-Rel transformed cells, gene expression patterns in normal and v-Rel transformed cells were compared by mRNA differential display. Northern blotting analysis with radiolabeled cDNAs from differential display confirmed the reproducible differential expression of 10 transcripts in v-Rel transformed cells. One of the identified genes, termed ch-IAP1, encodes a chicken homolog of the inhibitor-of-apoptosis protein (IAP) family. ch-IAP1 contains N-terminal baculovirus IAP repeats (BIR), the hallmark of IAPs, and has a C-terminal RING finger motif commonly present in the other IAPs. Like other IAPs, ch-IAP1 is expressed predominantly in the cytoplasm of cells. ch-IAP1 is highly expressed in v-Rel transformed fibroblasts, B- and T-cell lines, and spleen cell lines. In contrast, ch-IAP1 expression levels were low in chicken cell lines transformed by several other unrelated tumor viruses. Additionally, ch-IAP1 expression is downregulated in temperature-sensitive (ts) v-Rel transformed spleen cells at the nonpermissive temperature. Overexpression of the full-length ch-IAP1 suppresses mammalian cell apoptosis induced by the interleukin-1-converting enzyme (ICE), a member of the mammalian caspase family of cysteine proteases. Furthermore, expression of exogenous ch-IAP1 inhibits apoptosis of ts v-Rel transformed spleen cells at the nonpermissive temperature.
Insights
The v-Rel oncoprotein activates oncogenic transformation and inhibits apoptosis. Researchers identified ch-IAP1, a novel inhibitor-of-apoptosis protein, which is highly expressed in v-Rel transformed cells and suppresses apoptosis.
Area of Science:
- Molecular Biology
- Oncology
- Cell Biology
Background:
- The v-Rel oncoprotein, a member of the Rel/NF-kappaB transcription factor family, is known to induce oncogenic transformation and inhibit apoptosis.
- Identifying cellular genes aberrantly expressed in v-Rel transformed cells is crucial for understanding oncogenesis.
Purpose of the Study:
- To identify and characterize novel cellular genes differentially expressed in v-Rel transformed cells.
- To investigate the role of the identified chicken inhibitor-of-apoptosis protein 1 (ch-IAP1) in apoptosis regulation.
Main Methods:
- Differential display of mRNA was used to compare gene expression patterns between normal and v-Rel transformed cells.
- Northern blotting confirmed the differential expression of 10 transcripts, including ch-IAP1.
- Functional assays were performed to assess the effect of ch-IAP1 on apoptosis.
Main Results:
- A novel gene, ch-IAP1, encoding a chicken homolog of the inhibitor-of-apoptosis protein (IAP) family, was identified.
- ch-IAP1 exhibits high expression in v-Rel transformed cells and contains characteristic IAP domains (BIRs and a RING finger).
- Overexpression of ch-IAP1 suppressed apoptosis induced by caspase-1 (ICE) in mammalian cells and in temperature-sensitive v-Rel transformed cells.
Conclusions:
- ch-IAP1 is a novel inhibitor-of-apoptosis protein upregulated by v-Rel oncoprotein.
- ch-IAP1 plays a significant role in inhibiting apoptosis, contributing to v-Rel-mediated oncogenic transformation.
- ch-IAP1 represents a potential therapeutic target for cancers driven by v-Rel or related pathways.