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Identification of alternatively spliced Act1 and implications for its roles in oncogenesis
Yi-Feng Xia1, Yi-Dan Li, Xiaoxia Li
1Laboratory of Molecular Cell Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, 320 Yue-Yang Road, Shanghai, China.
Abstract:
Act1 (also called CIKS) is a recently identified molecule, which activates NF-kappaB and AP-1. Here, we identified alternatively spliced Act1 that lacked the exon 2 encoding the first nine amino acids in the amino terminus of the protein. Compared to full-length Act1, this truncated Act1 appeared to be equally active. We demonstrated further that only the spliced Act1 was detected in cDNA libraries derived from human fetal brain, liver, leukocytes, and bone marrow. In contrast, both the spliced and full-length Act1 templates were detected in a variety of human cancer cell lines. The expression of both the spliced and full-length transcripts was detected at 4-h time point, following the treatment of endothelial cells with tumor necrosis factor-alpha, interleukin-1beta or bacterial endotoxin. Notably, the dominant amounts of the spliced Act1 over the full-length Act1 were amplified from both the cancer cell mRNAs and the stimulated endothelial cell mRNAs. Taken together with the act1 chromosome localization at the 6q21 subregion, our findings indicate that the newly identified alternatively spliced Act1 is a major transcript of the molecule and that Act1 may play important roles in oncogenesis.
Insights
A newly identified alternatively spliced Act1 molecule, equally active as full-length Act1, is a major transcript. This spliced Act1 may play significant roles in oncogenesis and is predominantly found in cancer cells.
Area of Science:
- Molecular Biology
- Cell Biology
- Oncology
Background:
- Act1 (CIKS) is a molecule known to activate NF-kappaB and AP-1 signaling pathways.
- Alternative splicing is a key mechanism regulating gene expression and protein function.
Purpose of the Study:
- To identify and characterize alternatively spliced variants of Act1.
- To investigate the expression patterns and potential roles of Act1 splice variants in human tissues and cancer.
Main Methods:
- Identification of alternatively spliced Act1 lacking exon 2 using cDNA libraries.
- Quantitative analysis of Act1 splice variant expression in normal tissues, cancer cell lines, and stimulated endothelial cells.
- Analysis of Act1 transcript levels following stimulation with TNF-alpha, IL-1beta, and bacterial endotoxin.
Main Results:
- An alternatively spliced Act1 variant, lacking the N-terminal exon 2, was identified and found to be equally active as full-length Act1.
- Spliced Act1 was the predominant transcript in normal human fetal tissues, while both spliced and full-length Act1 were detected in cancer cell lines.
- Stimulation of endothelial cells induced expression of both Act1 transcripts, with a notable dominance of the spliced variant in cancer and stimulated cells.
Conclusions:
- The alternatively spliced Act1 variant is a major transcript of the Act1 molecule.
- Act1, particularly its spliced form, may play a significant role in oncogenesis.
- The differential expression of Act1 splice variants suggests tissue-specific and context-dependent functions.