PURIFICATION OF THE MAJOR HISTOCOMPATIBILITY COMPLEX CLASS-I TRANSCRIPTION FACTOR-H2TF1 - THE FULL-LENGTH PRODUCT OF THE NFKB2 GENE

H2TF1 is a ubiquitous major histocompatibility complex (MHC) class I-s pecific transcription factor, which binds to the palindromic kappaB en hancer site upstream of MHC class I genes. Here we report that H2TF1 c onsists of a polypeptide with relative molecular mass 110,000, that co rresponds to the predicted 100-kDa product (NF-kappaB2 p100) encoded b y the candidate proto-oncogene nfkb2 (lyt-10). H2TF1 was purified by a novel affinity chromatography method and identified as the NF-kappaB2 p100 polypeptide by peptide sequencing as well as by reactivity with a specific antiserum. Purified H2TF1 binds the MHC kappaB site with hi gh affinity (K(D) = 3 x 10(-11) M), in contrast with previous reports that NF-kappaB2 p100 did not bind DNA.