Overexpression and reactivation of binding activity of the recombinant CTF/NF-1 transcription factor

The transcription factor CTF/NF-1 is a multifunctional cellular protein which participates in the expression of host and viral genes and in the replication of viral DNA. A procedure was developed to obtain recombinant CTF/NF-1 protein in order to help identify the binding sites of CTF/NF-1 protein in the regulatory region of viral sequences. Cloning and expression of the CTF/NF-1 gene downstream from a T7 RNA polymerase promoter resulted in an insoluble protein produced in Escherichia coli. Specific binding by the recombinant CTF/NF-1 protein to its cognate recognition site was obtained only after a denaturation and renaturation procedure. No special chromatography steps were required to obtain a rCTF/NF-1 preparation which could be used for our binding studies. Specific binding was detected with an NF-1 oligonucleotide and with viral DNA templates. Binding to the viral DNA sequences was identical to that previously published with biochemically purified cellular CTF/NF-1 protein.