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

The in vivo recruitment of PCAF to the XBP-1S endogenous target genes was examined next. Cells were transfected with a PCAF expression plasmid and an indicated vector (i.e. empty, XBP-1U, and XBP-1S plasmids). Distribution of PCAF and XBP-1 on the promoters of BiP and CHOP was analyzed by quantitative ChIP. Fewer XBP-1 and PCAF proteins were located on BiP and CHOP genes when XBP-1U was overexpressed ( Figure 7A and B) . In the XBP-1S/PCAF co-transfected cells, more XBP-1S proteins were found to bind to the promoter region of BiP and CHOP genes ( Figure 7A and B). It was expected since overexpression of XBP-1S activated the transcription of BiP and CHOP ( Figure 6B ). In addition, a 3-fold increase in PCAF binding to BiP and CHOP genes was detected in the XBP-1S/PCAF co-expressing cells ( Figure 7A and B) , providing the evidence that PCAF was recruited to BiP and CHOP promoters through the interaction with XBP-1S.