Interferon regulatory factor-1 (IRF-1) is a vertebrate transcription factor that plays significant roles in cell cycle regulation, anti-viral response, tumor suppression and immune response. High-level expression of recombinant IRF-1 at 37 °C leads to the formation of insoluble aggregates (insoluble fraction) in Escherichia coli (E. coli), which usually devoid of biological activity. In this study, we use chemical additives such as mannitol, proline, L-arginine and CTAB (cetyl trimethly ammonium bromide) at the recommended concentration during cell lysis to aid in solubility at 37 °C. The use of additives resulted in the increased solubility of the recombinant glutathione S-transferase-linked human IRF-1, with L-arginine being most effective. Here, we developed an efficient process for the manufacturing of soluble IRF-1 with the aid of minimizing the formation of degradation products and optimizing protein purification conditions. This result was further confirmed by western blot with anti-GST and anti-IRF-1 polyclonal antibodies. The functionality of GST-huIRF-1 was attained by elerophoretic mobility shift assay study as a clear band shifting showed with virus response element-Interferon beta (VRE-IFNβ) promoter region. Taken together, the biological activity of purified GST-huIRF-1 was also optimized and confirmed by supershift assay concluded that GST-huIRF-1 interacts with the VRE motif of IFNβ promoter that reflected to require for IFNβ gene regulation. We describe a straightforward approach for the production of absolutely soluble and biologically active IRF-1 in E. coli. This method can be further used for the study of other recombinant proteins and this study will pave way for the analysis of IRF-1 function in vitro.
Keywords: DNA binding domain; EMSA; GST fusion protein; Interferon regulatory factors; Recombinant protein.