title: Protein that binds to the distal, but not to the proximal, CCAAT of the human thymidine kinase gene promoter.
abstract: Mobility shift assays were used to examine protein binding to the human TK gene CCAAT boxes. Similar protein binding patterns were observed with probes containing either the proximal or distal CCAAT. However, probes containing both CCAAT boxes in which one of the CCAAT boxes was inactivated by mutation did not demonstrate identical binding patterns. One of the complexes formed with the longer probes was only observed when the distal CCAAT was intact. This species was not formed with probes that only contained an intact proximal CCAAT, and its formation could only be competed by oligonucleotides containing the distal CCAAT motif. This observation reveals the existence of a protein that can bind to the distal, but not to the proximal, CCAAT of the human TK promoter. This protein may account for the previous observation that the two CCAAT motifs are not functionally equivalent. The protein that binds to the distal, but not to the proximal, CCAAT (DTK-CBP) was also present in two human cell lines. Significantly more DTK-CBP was present in nuclear extracts of HepG2 and WI38 cells than in TK-ts13 cells. However, this protein was not observed in three different murine cell lines and one primary culture. Its abundance in some human cell lines suggests it might modulate the expression of human TK mRNA in cells that express this protein.
authors.affiliation: Department of Molecular Genetics and Microbiology, University of Medicine and Dentistry of New Jersey, Robert Wood Johnson Medical School, Piscataway 08854, USA.
authors.forename: K E
authors.initials: KE
authors.lastname: Lipson
authors.forename: G
authors.initials: G
authors.lastname: Liang
authors.forename: L
authors.initials: L
authors.lastname: Xia
authors.forename: X
authors.initials: X
authors.lastname: Gai
authors.forename: M B
authors.initials: MB
authors.lastname: Prystowsky
authors.forename: X
authors.initials: X
authors.lastname: Mao
mesh_terms: D016475:3T3 Cells; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D001667:Binding, Competitive; D022762:CCAAT-Enhancer-Binding Proteins; D002478:Cells, Cultured; D006224:Cricetinae; D017077:Culture Media, Conditioned; D015342:DNA Probes; D004268:DNA-Binding Proteins / Q000378:metabolism* / Q000502:physiology*; D006801:Humans; D008647:Mesocricetus; D051379:Mice; D008807:Mice, Inbred BALB C; D008969:Molecular Sequence Data; D009154:Mutation; D009687:Nuclear Proteins / Q000378:metabolism*; D009841:Oligonucleotides / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000502:physiology*; D011485:Protein Binding; D013937:Thymidine Kinase / Q000235:genetics* / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism
chemical_list: D022762:CCAAT-Enhancer-Binding Proteins; D017077:Culture Media, Conditioned; D015342:DNA Probes; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D009841:Oligonucleotides; D014157:Transcription Factors; D013937:Thymidine Kinase