Transcriptional regulation of an Arabidopsis gene encoding a CCT domain-containing protein during endoplasmic reticulum stress

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In eukaryotic cells, accumulation of unfolded proteins in the endoplasmic reticulum (ER) triggers the transcriptional induction of ER-resident molecular chaperones and folding enzymes to maintain cellular homeostasis, termed the ER stress response or the unfolded protein response (UPR). In this study we focused on a putative transcriptional regulator of Arabidopsis thaliana whose transcripts accumulate in response to the ER stress inducer tunicamycin. This gene, designated as TCR1 (tunicamycin-induced CONSTANS-like-related 1), encodes a predicted protein of 195 amino acids with a plant-specific CCT (CONSTANS, CONSTANS-like, TOC1) domain considered to function in transcriptional regulation. In a dual-luciferase assay using Arabidopsis protoplasts, we showed that induction of the TCR1 gene by tunicamycin is independent of a nucleotide sequence similar to the cis-element ER stress response element on its promoter. Our result further indicates that this induction could be mediated by the transcription factor AtbZIP60. This study is a first step to understand the role of TCR1 in the Arabidopsis ER stress response.
2008-09-01