[Proteins, interacting with the promotor of the immunoglobulin kappa gene]

Two octanucleotide binding protein factors (mOct-1 and mOct-2A) are detected in nuclear extracts of lymphoid NS/0 cell line. These proteins, corresponding to human Oct-1 and Oct-2A nuclear factors, were purified by ion exchange and heparin-agarose chromatography. With retardation assay technique it was shown that mOct-2A factor at all steps of purification contains tightly bound protein, dissociating in the presence of a nonspecific native DNA. This octa-protein-associated factor (OAF) has low affinity to DNA and is not able to bind specifically the promoter of kappa-gene. However it interacts with DNA together with mOct-2A in highly specific manner but does not form complexes with mOct-1 and mOct-2B factors. Since OAF can be attached specifically only to mOct-2A (which play an essential role in initiation of kappa-gene transcription) this attachment may be considered as necessary for its recognition as a specific transcription factor. The ability of OAF like alpha TIF factor (specifically interacting with Oct-1) to discriminate between the Oct proteins, recognizing the same cis-acting oct-elements, shows how the non-DNA-binding transcription factors can influence differentially the transcription by two proteins binding to the same DNA sequences.