Tandemly reiterated negative enhancer-like elements regulate transcription of a human gene for the large subunit of calcium-dependent protease.

Calcium-dependent protease (CANP, Calpain) is an intracellular protease involved in essential cellular functions mediated by calcium. To understand the mechanism regulating the expression of CANP at the transcriptional level, we isolated a human gene for the large subunit of mCANP (CANP mL) and analyzed its 5'-region. The transcription initiation sites were mapped to multiple positions (-142 to -103, A of initiation ATG as +1). The upstream region lacks typical promoter elements such as TATA and CAAT boxes and is characterized by its high GC content (-300 to -20, 70% GC content). Functional analyses of the 5'-region by a transient expression assay on HeLa cells revealed that the region (-202 to -80) has a promoter activity. The upstream half of the promoter region (-202 to -130) acts as an upstream promoter element in an orientation-independent manner. Upstream of the promoter region are tandemly reiterated multiple regulatory regions (-2.5k to -690, -690 to -460, -460 to -260, and -260 to -202), each of which negatively regulates the CANP mL gene promoter as well as heterologous promoters in an orientation-independent manner. The presence of a cellular factor(s) mediating the action of these positive (promoter) and negative regulatory elements was suggested by an in vivo competition assay. The negative regulation of transcription mediated by these reiterated cis-acting elements and trans-acting factor(s) may play an essential role in the expression of the CANP mL gene.