Abstract 2344 Increase in Hexim1 phosphorylation by JAK2 in DU145 prostate cancer cell

Hexamethylene bis-acetamide inducible-1 protein (Hexim1) is an inhibitor of RNA polymerase II dependent transcription elongation and serves as an RNA-dependent regulatory protein hub. Therefore, it is involved in many important cellular processes such as differentiation, development, and inflammation. Furthermore, Hexim1 has been demonstrated to play a pivotal role in the progression of prostate cancer, with notable increases in Hexim1 phosphorylation observed in the androgen independent DU145 prostate cancer cell line. Consequently, unraveling the mechanisms underlying Hexim1 phosphorylation is crucial for comprehending its involvement in cancer. Hexim1 has shown to activate JAK/Stat (Janus Kinase / Signal Transducer and Activator of Transcription) signaling pathway by inhibiting expression of SOCS3, which suggests possible interaction between Hexim1 and JAK2. To investigate direct interaction between Hexim1 and Jak2, both proteins were expressed and purified using His-tagged recombinant constructs. Our findings from the western blot analysis, conducted with antibodies selectively targeting the phosphorylated tyrosine residue within the YXXL motif, indicate that Hexim1 undergoes phosphorylation mediated by JAK2. We further explored the impact of Hexim1 phosphorylation in the context of tumor growth and progression. Our results showed increase in Hexim1 phosphorylation by JAK2 in androgen independent DU145 human prostate cancer cell lines. Hexim1 phosphorylation by JAK2 is significant due to its potential role in oncogenesis and other diseases. Understanding this interaction is crucial for developing targeted therapies and could provide insights into the molecular mechanisms underlying various pathologies.