Generation of biologically active recombinant human OCT4 protein from E. coli

An Insight into the Role of GLIS1 in Embryonic Development, iPSC Generation, and Cancer

The curiosity to discover transcription factors to reprogram somatic cells to induced pluripotent stem cells (iPSCs) resulted in the identification of a reprogramming factor, Gli-similar transcription factor GLIS1. This proline-rich Kruppel-like zinc finger transcription factor has a role in embryonic development, iPSC generation, and cancer. The spatial and temporal expression of GLIS1 during embryonic development implicates that it can control gene expression at specific developmental stages. Moreover, GLIS1 in combination with OCT4, SOX2, and KLF4 reprogramming factors resulted in an increase in reprogramming efficiency, giving rise to primarily bona fide iPSCs. Mutations in the GLIS1 gene are associated with several types of tumors and cancers, and it shows a tissue-specific function where it acts either as an oncogene or as a tumor suppressor gene. This review gives a comprehensive overview of GLIS1 and its important role in embryonic development, cancer, and the generation of iPSCs.

Biological activity of recombinant human PDX1 protein produced from Escherichia coli

Pancreatic and duodenum homeobox 1 (PDX1) is considered as a pivotal transcription factor that acts as a "master regulator" in pancreatogenesis and maintenance of β-cells. Earlier study has reported that PDX1 also functions as a tumor suppressor in human gastric cancer cells by inhibiting cell growth. Here, we report the bioactivity of the purified human PDX1 fusion protein using various assays like cell migration, proliferation, cell cycle analysis, and gene expression. In cancer cells, recombinant PDX1 protein reduced cell migration and proliferation, and arrested cell growth by inducing apoptosis in gastric cancer cells. In pancreatic ductal cancer cells, the application of the PDX1 protein resulted in the induction of insulin gene expression. The results of these experiments demonstrate the biological activity imparted by recombinant human PDX1 fusion protein on gastric and pancreatic cancer cells and its usefulness as a biological tool to elucidate its function in various cellular processes.

Production of Bioactive Human PAX4 Protein from E. coli

Paired box 4 (PAX4) is a pivotal transcription factor involved in pancreatogenesis during embryogenesis, and in adults, it is key for β-cell proliferation and survival. Additionally, PAX4 also functions as a tumor suppressor protein in human melanomas. The present study demonstrates the production of bioactive recombinant human PAX4 transcription factor. At first, the inserts (PAX4 protein-coding sequence having tags at either ends) were cloned in an expression vector to give rise to pET28a(+)-HTN-PAX4 and pET28a(+)-PAX4-NTH genetic constructs, and these were then transformed into Escherichia coli (E. coli) for their expression. The HTN-PAX4 and PAX4-NTH fusion proteins produced were purified with a yield of ~ 3.15 mg and ~ 0.83 mg, respectively, from 1.2 L E. coli culture. Further, the secondary structure retention of the PAX4 fusion proteins and their potential to internalize the mammalian cell and its nucleus was demonstrated. The bioactivity of these fusion proteins was investigated using various assays (cell migration, cell proliferation and cell cycle assays), demonstrating it to function as a tumor suppressor protein. Thus, this macromolecule can prospectively help understand the function of human PAX4 in cellular processes, disease-specific investigations and direct cellular reprogramming.

Generation of a recombinant version of a biologically active cell-permeant human HAND2 transcription factor from E. coli

Transcription factor HAND2 has a significant role in vascularization, angiogenesis, and cardiac neural crest development. It is one of the key cardiac factors crucial for the enhanced derivation of functional and mature myocytes from non-myocyte cells. Here, we report the generation of the recombinant human HAND2 fusion protein from the heterologous system. First, we cloned the full-length human HAND2 gene (only protein-coding sequence) after codon optimization along with the fusion tags (for cell penetration, nuclear translocation, and affinity purification) into the expression vector. We then transformed and expressed it in Escherichia coli strain, BL21(DE3). Next, the effect (in terms of expression) of tagging fusion tags with this recombinant protein at two different terminals was also investigated. Using affinity chromatography, we established the one-step homogeneous purification of recombinant human HAND2 fusion protein; and through circular dichroism spectroscopy, we established that this purified protein had retained its secondary structure. We then showed that this purified human protein could transduce the human cells and translocate to its nucleus. The generated recombinant HAND2 fusion protein showed angiogenic potential in the ex vivo chicken embryo model. Following transduction in MEF2C overexpressing cardiomyoblast cells, this purified recombinant protein synergistically activated the α-MHC promoter and induced GFP expression in the α-MHC-eGFP reporter assay. Prospectively, the purified bioactive recombinant HAND2 protein can potentially be a safe and effective molecular tool in the direct cardiac reprogramming process and other biological applications.

Identification of Optimal Expression Parameters and Purification of a Codon-Optimized Human GLIS1 Transcription Factor from Escherichia coli

GLIS1 has multiple roles in embryonic development and in deriving induced pluripotent stem cells by aiding signaling pathways and chromatin assembly. An inexpensive and simple method to produce human GLIS1 protein from Escherichia coli (E. coli) is demonstrated in this study. Various parameters such as codon usage bias, E. coli strains, media, induction conditions (such as inducer concentration, cell density, time, and temperature), and genetic constructs were investigated to obtain soluble expression of human GLIS1 protein. Using identified expression conditions and an appropriate genetic construct, the human GLIS1 protein was homogeneously purified (purity > 90%) under native conditions. Importantly, the purified protein has upheld a stable secondary structure, as demonstrated by circular dichroism spectroscopy. To the best of our knowledge, this is the first study to report the ideal expression conditions of human GLIS1 protein in E. coli to achieve soluble expression and purification under native conditions, upholding its stable secondary structure post-purification. The biological activity of the purified GLIS1 fusion protein was further assessed in MDA-MB-231 cells. This biologically active human GLIS1 protein potentiates new avenues to understand its molecular mechanisms in different cellular functions in various cancers and in the generation of induced pluripotent stem cells.