Expression, purification and characterization of TAT-high mobility group box-1A peptide as a carrier of nucleic acids.

High mobility group box 1 (HMGB1) is an abundant nuclear protein that binds to double-stranded DNA. HMGB1 is composed of high mobility (HMG) box A, box B, and C-terminal acidic regions. In this study, a recombinant TAT linked HMGB1 box A (rTAT-HMGB1A) peptide was expressed, purified, and characterized as a carrier of nucleic acids. The HMGB1A cDNA was amplified by PCR, and cloned into the pET21a expression vector with the TAT domain located at the N-terminus. The rTAT-HMGB1A peptide was overexpressed and purified using Nickel affinity chromatography. A recombinant HMGB1A (rHMGB1A) peptide without the TAT domain was also overexpressed and purified as a control. In gel retardation assays, both the rHMGB1A and rTAT-HMGB1A peptides formed complexes with DNA equally well. However, transfection assays showed that the rTAT-HMGB1A peptide had a higher gene transfer efficiency than rHMGB1A. Finally, rTAT-HMGB1A had no cytotoxicity to HEK 293 cells suggesting that rTAT-HMGB1A may be useful as a non-toxic gene delivery carrier.