[Protein factors, interacting with the octamer sequence of immunoglobulin genes]

Nuclei of different cell lines contain protein factors interacting with octamer ATTTGCAT. Fragment k53 of kappa-gene promoter region was used as DNA-probe. The factors from lymphoid cells yield a DNA/protein complex with mobility B0. The proteins are referred to as HF-B0. The nonspecific ubiquitous factor present in many non-lymphoid cells (for instance, HeLa cells) interacts with the probe to produce a complex whose mobility is much lower. The protein NF-B0 was isolated from the nuclear extract of myeloma MOPC21 cells. It was purified by chromatography on ion exchangers, hydroxylapatite, heparin-Sepharose and affinity sorbent containing a synthetic octamer sequence. At all the steps of purification, protein fractions were chosen for their ability to interact selectively with the octamer yielding a complex with the mobility B0. As a result, NF-B0 protein (60 +/- 2)kDa was purified 6.10(4) times to the electrophoretically homogeneous state. Purified factor NF-B0 selectively interacts with the octamer.