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XBP‐1, a novel HTLV‐1 Tax binding protein, activates HTLV‐1 basal and Tax‐activated transcription
Author(s) -
Chao ShengHao,
Ku Sebastian,
Lee Jialing,
Lau Joanne,
Gurumurthy Meera,
Ng Raymond,
Lwa Siew Hui,
Lee Joseph,
Klase Zachary,
Kashanchi Fatah
Publication year - 2008
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.22.1_supplement.782.12
Subject(s) - creb , unfolded protein response , transcription factor , endoplasmic reticulum , activating transcription factor , transcription (linguistics) , biology , microbiology and biotechnology , gene isoform , gene , biochemistry , linguistics , philosophy
X‐box binding protein 1 (XBP‐1) is a CREB/ATF (cyclic AMP response element binding protein/activating transcription factor) family transcription factor. XBP‐1 plays a major role in the cellular unfolded protein response (UPR), which is triggered by accumulation of unfolded or malfolded proteins in the endoplasmic reticulum. There are two XBP‐1 isoforms in cells, the spliced XBP‐1S and the unspliced XBP‐1U. In 1990, XBP‐1U (also known as TREB5) was identified as one of the cellular proteins binding to the Tax‐responsive element of human T‐lymphotropic virus type 1 (HTLV‐1). However, this study was carried out before the discovery of XBP‐1S. Here we identify XBP‐1S as a transcription activator of HTLV‐1. Compared to XBP‐1U, XBP‐1S demonstrates stronger activating effects on both basal and Tax‐activated HTLV‐1 transcription. Our results show that both XBP‐1S and XBP‐1U interact with Tax and bind to HTLV‐1 LTR in vivo. In addition, elevated mRNA levels of XBP‐1 and several UPR genes are detected in the HTLV‐1‐infected T cell lines, suggesting that HTLV‐1 infection may trigger UPR in the host cells. We also identify Tax as a positive regulator of XBP‐1 gene expression. Collectively, our study demonstrates a novel host‐viral interaction between a cellular factor XBP‐1 and HTLV‐1 transcription.