PCAF interacts with XBP-1S and mediates XBP-1S-dependent transcription

Lew, Qiao Jing; Chu, Kai Ling; Lee, Jialing; Koh, Poh Ling; Rajasegaran, Vikneswari; Teo, Jin Yuan; Chao, Sheng-Hao

We previously demonstrated that XBP-1S, a member of CREB/ATF family proteins, stimulates basal and Tax-activated HTLV-1 transcription (26) . It has been reported that two histone acetyltransferases (HATs), PCAF and p300, are required to activate HTLV-1 transcription through three 21-bp repeats known as Taxresponsive element (TRE) located with the HTLV-1 promoter (30) . Each TRE contains a binding site for CREB/ATF proteins, suggesting a potential functional connection between HATs and XBP-1S. We first investigated the interaction between PCAF and two XBP-1 isoforms. Cells were transfected with an XBP-1S or XBP-1U expression plasmid followed by IP analyses Figure 1 . PCAF associates with XBP-1S. (A) 293T cells were transfected with an expression plasmid to ectopically express XBP-1S, XBP-1U and CREB1, respectively. IP was performed using the cell lysates prepared from the transfected cells and the indicated antibodies. Normal IgG (IgG) was used as a negative control. The immunoprecipitated complexes and the protein inputs were analyzed by western blotting. (B) The cell lysates of XBP-1S expressing cells were used for IP with an anti-PCAF antibody. The presence of XBP-1S in the immunoprecipitates was determined by western blotting. (C) Cells were co-transfected with a p300 expression vector and an indicated plasmid (i.e. XBP-1S, XBP-1U, and CREB1 plasmids, respectively). IP was carried out using an anti-p300 antibody followed by western blotting.