title: An enhancer in the first intron of the human purine nucleoside phosphorylase-encoding gene.
abstract: In previous studies characterizing intron-dependent expression of the human purine nucleoside phosphorylase-encoding gene (PNP), we identified a putative enhancer sequence in the first intron which was capable of mediating increased cat reporter gene expression in transfected murine NIH 3T3 cells in a position- and orientation-independent manner. In order to further characterize this enhancer activity, the nucleotide sequence was determined for the region of intron 1 to which this activity was originally ascribed. The sequence was analyzed for the presence of binding sites for known transcription factors, but none were identified. A 444-bp downstream portion of the intron-1 sequence enhanced cat expression either in conjunction with a human PNP promoter sequence or with a 105-bp heterologous herpes simplex virus thymidine kinase (TK) promoter. Nested deletions of the downstream intron-1 sequence fused to a TK::cat fusion gene localized the enhancer activity to a 170-bp sequence in intron 1. A 154-bp HgiAI fragment (bp 424 to 577 of intron 1) excised from this region contained enhancer activity which varied directly with the number of fragments inserted upstream from the TK::cat fusion gene. However, inversion of the HgiAI fragment in a PNP abbreviated gene, or relocation of the HgiAI fragment from intron 1 to a position upstream from the PNP promoter, reduced or eliminated PNP expression. The effect of the intron-1 enhancer element on PNP expression is thus maximized in a position- and orientation-dependent manner.
authors.affiliation: Institute of Human Genetics, University of Minnesota, Minneapolis 55455.
authors.forename: J J
authors.initials: JJ
authors.lastname: Jonsson
authors.forename: A
authors.initials: A
authors.lastname: Converse
authors.forename: R S
authors.initials: RS
authors.lastname: McIvor
mesh_terms: D016475:3T3 Cells; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D004247:DNA; D004274:DNA, Recombinant; D004742:Enhancer Elements, Genetic; D017930:Genes, Reporter; D006801:Humans; D007438:Introns; D051379:Mice; D008969:Molecular Sequence Data; D011683:Purine-Nucleoside Phosphorylase / Q000235:genetics*; D014162:Transfection
chemical_list: D004274:DNA, Recombinant; D004247:DNA; D011683:Purine-Nucleoside Phosphorylase