Investigating the effects of PKNOX2 and its interactors in P53 pathway regulation in bone marrow mesenchymal stem cells

Mesenchymal Stem Cells (MSC) are good platforms to study in-vitro molecular mechanisms. Like all cells, MSCs detect and respond to various stimuli with molecular signal mechanisms. p53 signal pathway is a well-known molecular mechanism for transduction of cellular stresses such as DNA damage. p53 signal pathway is heavily regulated in both transcription and post-translational modification of its elements. PKNOX2, a member of TALE homeodomain protein family, is a transcriptional activator of p53. In a previous study by Günel-Özcan lab group, protein interactors of PKNOX2 were determined by proteomics analysis following Co-immunoprecipitation. For this study, the interactors of PKNOX2 from proteomics was compared with the interactors of p53 obtained from BioGRID database and two proteins, DNAJA1 and RPS3 were selected as possible common interactors with possible signaling functions under stress conditions. In this study, three different sources of DNA damage stress, H2O2, DEB and γ-Irradiation were applied to human Bone Marrow Mesenchymal Stem Cells (BM-MSC) and protein expression levels of DNAJA1, RPS3, p53 and PKNOX2 were measured with western blotting. PKNOX2 expression was found to be decreasing in DEB and γ-Irradiation significantly, p53 expression was found to be increasing in H2O2 application significantly. Expression levels of RPS3 and DNAJA1 were found to be stable under stress. Co-Immunoprecipitation was performed with anti-PKNOX2 and anti-p53 antibodies but the results were inconclusive for any interactions. Co-immunoprecipitation protocol was improved. Further study with this improved protocol is needed to unveil these interactions.