An extensive repeat structure down-regulates human monoamine oxidase A promoter activity independent of an initiator-like sequence.
The 5' flanking sequence of the human monoamine oxidase A (MAO A) gene consists of an extensive repeat structure. Two 90-bp repeats (I and II) were found in the core promoter (the 0.24-kb PvuII/DraII fragment), each containing two Sp1 binding sites. An additional six repeats were found, five of which (III-VII) were upstream and one (-I) downstream of the core promoter. Using transient transfection assay with a human growth hormone reporter gene, we found that the upstream repeating units III-VII (in a 0.78-kb BamHI/DraII fragment) down-regulate core promoter activity to 13 +/- 10% in a human glioma cell line (1242 MG) and 2 +/- 1% in a cervical carcinoma cell line (HeLa), respectively. The 0.24-kb core promoter activity was taken as 100%. Addition of the initiator (Inr)-like sequence to this 0.78-kb fragment (0.82-kb BamHI/-17 fragment) still showed decreased promoter activity (10 +/- 9% in 1242 MG cells and 8 +/- 1% in HeLa cells). Thus, the upstream sequence down-regulates promoter activity with or without the Inr-like sequence. When the Inr-like sequence was added to the core promoter (0.28-kb PvuII/-17 fragment), the promoter activity decreases significantly in both 1242 MG (55 +/- 6%) and HeLa (60 +/- 10%) cells. These results suggest that although the Inr-like sequence is present in the human MAO A promoter, it acts as a negative cis element instead of a transcription initiator.
Zhu
Q
Q
Department of Molecular Pharmacology and Toxicology, Pharmaceutical Sciences Center, and University of Southern California, Los Angeles 90033, U.S.A.
Shih
J C
JC
D001483:Base Sequence; D003062:Codon / Q000235:genetics; D018387:Codon, Initiator / Q000235:genetics; D004247:DNA / Q000235:genetics; D006801:Humans; D008969:Molecular Sequence Data; D008995:Monoamine Oxidase / Q000235:genetics*; D011401:Promoter Regions, Genetic / Q000235:genetics*; D012091:Repetitive Sequences, Nucleic Acid
D003062:Codon; D018387:Codon, Initiator; D004247:DNA; D008995:Monoamine Oxidase