[Factors interacting with promoter region of immunoglobulin genes. Determination of the binding site boundaries].

The nuclear extracts of plasmacytomas producing antibodies were found to contain factors which formed complexes with the promoter fragment of the gene for immunoglobulin kappa-chains. The corresponding complexes found in the extracts of nonlymphoid cells had a different mobility. Two approaches were proposed for determining the boundaries of the region necessary for protein factors to be bound to DNA using nuclease Ba131. A 5'-ATTTGCAT-3' octanucleotide sequence was shown to be necessary for interaction with the protein nuclear factor in the studied plasmacytoma lines. The protein completely lost its affinity if at least one nucleotide was removed or substituted at the 5'- or 3'-end of this sequence. The procedures proposed for determining the precise boundaries of the sequence necessary for protein binding to DNA do not require a preliminary protein purification. The principles on which the procedures are based, set no limitations to their application to other systems used for studying the interaction of proteins with DNA.