期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2015
卷号：112
期号：9
页码：2900-2905
DOI：10.1073/pnas.1419703112
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：SignificanceIn metazoans, pausing of Pol II during early elongation is a widespread regulatory mechanism for transcription regulation. However, preinitiation complex (PIC) assembly is more important for transcription in plants. Chromatin remodeling and histone modifications are considered important for access of protein factors to the underlying DNA sequences. However, how histone modifications are specifically and timely generated at active promoters is less understood. COMPASS-like complex plays a critical role in PIC assembly and histone H3K4 trimethylation. We found that Arabidopsis transcription factors bZIP28/bZIP60 interact with COMPASS-like components both in vitro and in vivo. We present a general model on how histone H3K4 trimethylation is specifically formed during inducible gene expression by using the endoplasmic reticulum (ER) stress response system in Arabidopsis plants. Accumulation of unfolded or misfolded proteins causes endoplasmic reticulum (ER) stress, which activates a set of ER membrane-associated transcription factors for protein homeostasis regulation. Previous genome-wide chromatin immunoprecipitation analysis shows a strong correlation between histone H3K4 trimethylation (H3K4me3) and active gene expression. However, how the histone modification complex is specifically and timely recruited to the active promoters remains unknown. Using ER stress responsive gene expression as a model system, we demonstrate that sequence-specific transcription factors interact with COMPASS-like components and affect H3K4me3 formation at specific target sites in Arabidopsis. Gene profiling analysis reveals that membrane-associated basic leucine zipper (bZIP) transcription factors bZIP28 and bZIP60 regulate most of the ER stress responsive genes. Loss-of-functions of bZIP28 and bZIP60 impair the occupancy of H3K4me3 on promoter regions of ER stress responsive genes. Further, in vitro pull-down assays and in vivo bimolecular fluorescence complementation (BiFC) experiments show that bZIP28 and bZIP60 interact with Ash2 and WDR5a, both of which are core COMPASS-like components. Knockdown expression of either Ash2 or WDR5a decreased the expression of several ER stress responsive genes. The COMPASS-like complex is known to interact with histone methyltransferase to facilitate preinitiation complex (PIC) assembly and generate H3K4me3 during transcription elongation. Thus, our data shows that the ER stress stimulus causes the formation of PIC and deposition of H3K4me3 mark at specific promoters through the interaction between transcription factor and COMPASS-like components.
关键词：COMPASS-like ; ER stress ; H3K4 trimethylation ; transcription factor ; unfolded protein response
