Objective To screen the possible regulatory proteins showing the ability for interaction with serum response factor ( SRF) in the progress of myofibroblast activation, and to see if the proteinprotein interaction is contributing to induce the expression of smooth muscle αactin ( α-SMA) . Methods Phage display cDNA libraries were constructed from the transdifferentiated airway epithelial cells and parental cells. Phage clones were then selectively amplified during the biopanning procedure by using SRF as a bait protein for the two cDNA libraries. Following four rounds of biopanning, recovered cDNAs were sequenced and the obtained sequences were aligned by BLAST tool to select the candidate gene. PAI-RBP1 of the candidate gene was cloned and sub-cloned into pcDNA3. 0 plasmid. Transient transfection and RT-PCR analysis were performed for investigation of the expression of α-SMA. Results Three candidate proteinbinding partners, PAI-RBP1, Nucleolin, and HF1OO, were identified. Among them, PAI-RBP1 pcDNA3. 0 plasmid was subjected to transient co-transfection with SRF, showing up-regulation of α-SMA expression. Conclusions Combined with phage display technique, through protein-protein interaction between core transcription factor and unknown proteins to find a newtranscriptional regulator may serve as an effective strategy. Three novel SRF binding proteins were found from transdifferentiated cells. This study indicates that PAI-RBP1 involves in the activation of myofibroblast by induction of α-SMA expression.