title: Purification of nuclear factor I by DNA recognition site affinity chromatography.
abstract: Nuclear factor I (NF-I) is a cellular protein that enhances the initiation of adenovirus DNA replication in vitro. The enhancement of initiation correlates with the ability of NF-I to bind a specific nucleotide sequence within the viral origin of replication. We have developed a method for the purification of NF-I which is based upon the high affinity interaction between the protein and its recognition site. This approach may be generally applicable to the purification of other site-specific DNA binding proteins. The essential feature of the method is a two-step column chromatographic procedure in which proteins are first fractionated on an affinity matrix consisting of nonspecific (Escherichia coli) DNA and then on a matrix that is highly enriched in the specific DNA sequence that is recognized by NF-I. During the first step NF-I coelutes with proteins that have similar general affinity for DNA. During the second step NF-I elutes at a much higher ionic strength than the contaminating nonspecific DNA binding proteins. The DNA recognition site affinity matrix used in the second step is prepared from a plasmid (pKB67-88) that contains 88 copies of the NF-I binding site. This plasmid was constructed by means of a novel cloning strategy that generates concatenated NF-I binding sites arranged exclusively in a direct head to tail configuration. Using this purification scheme, we have obtained a 2400-fold purification of NF-I from crude HeLa nuclear extract with a 57% recovery of specific DNA binding activity. Throughout the purification procedure NF-I retained the ability to enhance the efficiency of initiation of adenovirus DNA replication in vitro. Electrophoresis of the purified fraction on sodium dodecyl sulfate-polyacrylamide gels revealed a population of related polypeptides that ranged in apparent molecular weight from 66,000 to 52,000. The native molecular weight of NF-I deduced from gel filtration and glycerol sedimentation studies is 55,000 and the frictional ratio is 1.3. These results suggest that NF-I exists as a globular monomer in solution.
mesh_terms: D000256:Adenoviridae / Q000235:genetics; D001483:Base Sequence; D001665:Binding Sites; D022762:CCAAT-Enhancer-Binding Proteins; D002846:Chromatography, Affinity; D002850:Chromatography, Gel; D004247:DNA / Q000378:metabolism*; D004261:DNA Replication; D004262:DNA Restriction Enzymes / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000302:isolation & purification*; D015245:Deoxyribonuclease BamHI; D015252:Deoxyribonucleases, Type II Site-Specific; D004591:Electrophoresis, Polyacrylamide Gel; D006367:HeLa Cells; D051839:NFI Transcription Factors; D009687:Nuclear Proteins; D010957:Plasmids; D014157:Transcription Factors; D051840:Y-Box-Binding Protein 1
chemical_list: D022762:CCAAT-Enhancer-Binding Proteins; D004268:DNA-Binding Proteins; D051839:NFI Transcription Factors; D009687:Nuclear Proteins; D014157:Transcription Factors; D051840:Y-Box-Binding Protein 1; C070856:YBX1 protein, human; D004247:DNA; D004262:DNA Restriction Enzymes; D015245:Deoxyribonuclease BamHI; C024388:CTGCAG-specific type II deoxyribonucleases; D015252:Deoxyribonucleases, Type II Site-Specific