The putative apoptosis inhibitor IEX-1L is a mutant nonspliced variant of p22(PRG1/IEX-1) and is not expressed in vivo

• Published in: Biochemical and biophysical research communications 1999-08, Vol.262 (1), p.139-145
• Main Authors: Schäfer, H, Arlt, A, Trauzold, A, Hünermann-Jansen, A, Schmidt, W E
• Format: Article
• Language: English
• Subjects: Alternative Splicing - drug effects; Alternative Splicing - genetics; Animals; Apoptosis; Apoptosis Regulatory Proteins; Base Sequence; Cell Line; Cell Nucleus - drug effects; Cell Nucleus - genetics; Cell Survival; Cricetinae; Cytoplasm - drug effects; Cytoplasm - genetics; Gene Expression - drug effects; Humans; Immediate-Early Proteins - chemistry; Immediate-Early Proteins - genetics; Immediate-Early Proteins - metabolism; Membrane Glycoproteins - chemistry; Membrane Glycoproteins - genetics; Membrane Glycoproteins - metabolism; Membrane Proteins; Molecular Sequence Data; Mutation; Neoplasm Proteins; NF-kappa B - metabolism; Protein Isoforms - chemistry; Protein Isoforms - genetics; Protein Isoforms - metabolism; RNA, Messenger - analysis; RNA, Messenger - genetics; Tetradecanoylphorbol Acetate - pharmacology; Transfection; Tumor Necrosis Factor-alpha - pharmacology
• ISSN: 0006-291X
• DOI: 10.1006/bbrc.1999.1131

IEX-1L has been claimed to act as an apoptosis inhibitor involved in NFkappaB-mediated survival in Jurkat cells [Wu et al. (1998) Science 281, 998-1001]. It represents a mutant nonspliced variant of the early response gene p22(PRG1/IEX-1) exhibiting one insertion and two deletions compared to the genomic sequence of p22(PRG1/IEX-1). Direct DNA sequencing of PCR products generated from human genomic DNA only detected the regular genomic sequence of p22(PRG1/IEX-1). No IEX-1L mRNA could be identified by RT-PCR analysis and subsequent DNA sequencing of total, nuclear, or cytoplasmic RNA fractions from PMA-stimulated Jurkat cells. The only functional transcript residing in the cytoplasm is regularly spliced p22(IEX-1/PRG1) mRNA. Substantial amounts of nonmutated nonspliced p22(IEX-1/PRG1) pre-mRNA were identified in the nucleus. Thus, IEX-1L seems to be a mutant variant of p22(IEX-1/PRG1) not existing in vivo. Antiapoptotic effects obviously represent transdominant negative inhibition of endogenous p22(PRG1/IEX-1) in Jurkat cells and several other tumor cell lines.