TP63 and squamous cell carcinoma: To confirm in vivo that PTBP1 binds to TP63 pre-mRNAs, we immunoprecipitated specifically PTBP1/RNA complexes from keratinocytes (HaCaT) or squamous cell carcinomas cell lines (SCC9) cell extracts and analyzed the pre-mRNA content of the complexes by RT-PCR (Fig. 5B and C).