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

Requirement for PCAF in the mediation of endogenous XBP-1S target genes, including BiP, CHOP and EDEM (4), was investigated. We performed QRT-PCR assays to determine the impact of PCAF on the activation of XBP-1S target genes by knocking down the expression of PCAF. Compared to the DNA transfection, co-transfection of DNA plasmids and siRNAs was much more cytotoxic (data not shown). Therefore, a shRNA plasmid against PCAF was used to co-transfect cells along with an XBP-1 expression vector. Effectiveness of the PCAF shRNA was confirmed by western blotting ( Figure 6A ). Overexpression of XBP-1S resulted in 3-to 4-fold increases in the mRNA levels of BiP, CHOP, and EDEM ( Figure 6B ). Co-transfection of the PCAF shRNA in the XBP-1S-expressing cells led to 35, 74 and 52% inhibition of BiP, CHOP, and EDEM transcription, respectively ( Figure 6B ), demonstrating the involvement of PCAF in the XBP-1S-dependent transcription.