Constitutive expression of the urokinase plasminogen activator gene in murine RAW264 macrophages involves distal and 5' non-coding sequences that are conserved between mouse and pig.

ABSTRACT

The 5' flanking regions of the mouse and pig urokinase plasminogen activator (uPA) genes were sequenced and sequence homology interrupted by repeat elements was found to extend to -4.6kb in pig and -6.6kb in mouse. A transient transfection procedure was devised for the murine macrophage cell line RAW264. Pig uPA promoter-CAT constructs were more active than mouse constructs in this assay. This contrast may involve sequence differences within 100 bp of the transcription start site. The selective deletion of distal regions of the promoter (greater than 2.6 kb upstream), and of a conserved element, 5'-AGGAGGAAATGAGG-TCA-3' around -2 kb greatly reduced the activity of reporter constructs in RAW264 cells. Electrophoretic mobility shift assays using the latter sequence identified a single nuclear protein complex. This element has been referred to as PEA3/AP1-like, but the complex did not comigrate with either AP1 or known proteins that bind polypurines (including the macrophage-specific factor PU-1) and was not competed by AP1 or polypurine oligonucleotides. uPA promoters contain multiple AP1 and AP2-like DNA sequences, which were recognised by nuclear proteins expressed constitutively in RAW264 cells. They also contain multiple binding sites for NF kappa B but activated NF kappa B was not expressed in RAW264 cells. The conserved, transcribed 5' non-coding sequences were also required for maximal gene expression. Hence, the uPA promoter contains multiple weak cis-acting elements distributed over 7.0 kb 5' to the translation start site.