Cloning of a coproporphyrinogen oxidase promoter regulatory element binding protein

Coproporphyrinogen oxidase [CPO] gene promoter regulatory element (CPRE) pl ays an important role in CPO gene regulation. To isolate a CPRE binding pro tein, we performed Southwestern screening of K562 cDNA expression library u sing CPRE as a probe and isolated a cDNA clone which encoded a novel protei n, Klp1 (K562 cell-derived leucine-zipper-like protein 1). Klp1 mRNA was hi ghly expressed in K562 cells, HeLa cells, and brain as a single transcript (1.4 kb), Gel mobility shift assays revealed that Klp1 specifically binds t o CPRE. Computational analysis revealed that Klp1 has a leucine-zipper-like structure, a Leu-X-X-Leu-Leu moth, and a putative nuclear localization sig nal in the basic amino acid rich region. Transfection of the Klp1 expressio n vector into THP-1 cells resulted in transcriptional activation of a repor ter construct containing CPRE. These results indicate that Klp1 is a DNA se quence-specific transcription factor that regulates gene expression of gene s that contain CPRE in their regulatory region. (C) 2000 Academic Press.