Regulation of C/EBP beta isoforms
Date Issued
2008
Date
2008
Author(s)
Ke, Jia-Yu
Abstract
C/EBP beta is a transcription factor that belongs to the C/EBP family and plays important roles in many cellular responses. C/EBP beta expression increases during endoplasmic reticulum (ER) stress, which is triggered by the accumulation of unfolded proteins in the ER. Three isoforms, LAP*, LAP and LIP, are translated at alternative initiation codons of an intronless mRNA. LAP* and LAP are transcriptional activators, while LIP is a dominant-negative repressor. The relative expression of three isoforms is critical for C/EBP beta-mediated gene transcription. This report showed that the expression of C/EBP beta isoforms changed in response to thapsigargin and low dose anisomycin, which can trigger ER stress. We also found novel protein bands triggered by anisomycin treatment. An out-of-frame AUG codon of small open reading frame (sORF) in mRNA has been reported that regulated LAP and LIP expression. In this report, our data supported the model that translation of LIP is mediated by re-initiation model, in which the 40S ribosomal subunit remains attached to the mRNA after termination of the uORF, and re-initiates scanning.
Subjects
C/EBP beta
anisomycin
thapsigargin
leaky scanning
re-initiation
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