Three DNase I hypersenstive sites have been identified in 12 kb of genomic PNA, 5′ of the enhancer of the human uPA gene. Hypersensitive site 3 (HS3) is a cluster of three sites, mapping approximately from - 3 to - 4 kb from the start of transcription. HS2 is located at approximately - 4.5 kb from the transcription start site, while HS1 is found at - 10.5 kb. HS2 and HS3 are present in all cell lines analysed (PC3, HeLa, uninduced and PMAInduced HepG2). Interestingly, HS1 is absent in uPA-negative HeLa cells, while it is present in uPA-producing PC3 and in the inducible HepG2 cells [both induced and uninduced). However, while in PC3 cells HS1 is represented by one band only, in induced and uninduced HepG2 cells the hypersensitive site is a cluster of three bands. Transient transfection assays in PC3 and HeLa cells with luciferase plasmids containing HS1, HS2 and HS3 sequences cloned upstream of a viral TK promoter show that HS3 has a moderate enhancer activity, while the effect of HS1 and HS2 is negligible. Interestingly, the region between HS2 and HS1 seems to have substantial enhancer activity in HeLa cells, while it is ineffective in PC3 cells. The different 'architecture' of HS1 in uPA expressing (PC3) and inducible (HepG2) cells and its absence in nonexpressing cells suggests a role in the the transcriptional activity of the uPA gene. The results indicate that HS2 and HS3 are constitutive hypersensitive sites in all the cell models used. HS2 may be merely a structural site, while HS3 is a putative enhancer.
|Number of pages||1|
|Issue number||SUPPL. 3|
|Publication status||Published - 1996|
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