title: Regulation of expression of nuclear and mitochondrial forms of human uracil-DNA glycosylase.
abstract: Promoters PA and PBin the UNG gene and alternative splicing are utilized to generate nuclear (UNG2) and mitochondrial (UNG1) forms of human uracil-DNA glycosylase. We have found the highest levels of UNG1 mRNA in skeletal muscle, heart and testis and the highest UNG2 mRNA levels in testis, placenta, colon, small intestine and thymus, all of which contain proliferating cells. In synchronized HaCaT cells mRNAs for both forms increased in late G1/early S phase, accompanied by a 4- to 5-fold increase in enzyme activity. A combination of mutational analysis and transient transfection demonstrated that an E2F-1/DP-1-Rb complex is a strong negative regulator of both promoters, whereas 'free' E2F-1/DP-1 is a weak positive regulator, although a consensus element for E2F binding is only present in PB. These results indicate a central role for an E2F-DP-1-Rb complex in cell cycle regulation of UNG proteins. Sp1 and c-Myc binding elements close to transcription start areas were positive regulators of both promoters, however, whereas overexpression in HeLa cells of Sp1 stimulated both promoters, c-Myc and c-Myc/Max overexpression had a suppressive effect. CCAAT elements were negative regulators of PB, but positive regulators of PA. These results demonstrate differential expression of mRNAs for UNG1 and UNG2 in human tissues.
authors.affiliation: UNIGEN Center for Molecular Biology, The Medical Faculty, Norwegian University of Science and Technology, N-7005 Trondheim, Norway.
authors.forename: T
authors.initials: T
authors.lastname: Haug
authors.forename: F
authors.initials: F
authors.lastname: Skorpen
authors.forename: P A
authors.initials: PA
authors.lastname: Aas
authors.forename: V
authors.initials: V
authors.lastname: Malm
authors.forename: C
authors.initials: C
authors.lastname: Skjelbred
authors.forename: H E
authors.initials: HE
authors.lastname: Krokan
mesh_terms: D017398:Alternative Splicing; D001483:Base Sequence; D002352:Carrier Proteins; D002453:Cell Cycle; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism; D002467:Cell Nucleus / Q000201:enzymology*; D004247:DNA / Q000235:genetics; D045647:DNA Glycosylases; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; D005260:Female; D015971:Gene Expression Regulation, Enzymologic; D006367:HeLa Cells; D006801:Humans; D007527:Isoenzymes / Q000235:genetics; D008297:Male; D008928:Mitochondria / Q000201:enzymology*; D016297:Mutagenesis, Site-Directed; D009699:N-Glycosyl Hydrolases / Q000235:genetics*; D011247:Pregnancy; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D056465:Retinoblastoma-Binding Protein 1; D014018:Tissue Distribution; D050680:Transcription Factor DP1; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D014162:Transfection; D051981:Uracil-DNA Glycosidase
chemical_list: D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; C493753:E2F1 protein, human; D007527:Isoenzymes; D012333:RNA, Messenger; D056465:Retinoblastoma-Binding Protein 1; D050680:Transcription Factor DP1; D014157:Transcription Factors; D004247:DNA; D045647:DNA Glycosylases; D009699:N-Glycosyl Hydrolases; D051981:Uracil-DNA Glycosidase