Transcription factor Sp1 is necessary and functional in regulating expression of oncogene ZNF703

Zinc finger protein 703 (ZNF703) is a putative oncogene in patients with the luminal B molecular subtype of breast cancer. Although the exact function of ZNF703 protein remains largely unknown, its expression and regulation have been implicated in several physiological and pathological processes. In the current study, for the first time, we identified and characterized the human ZNF703 gene promoter region. As a means of characterizing the transcription elements required for expression of ZNF703 protein at different stages, we cloned the promoter region of ZNF703 then created chimeric reporter plasmids for use in luciferase assays. A progressive deletion analysis of the ZNF703 gene's 5' and 3' -flanking regions revealed that the core promoter is located in a 256-bp region ranging from nt-539 to nt-283. Next, we examined the effects of site-specific mutations and treatment with mithramycin A to identify the functional Sp1 binding site, which was found to be located in a 447 bp region that ranged from nt-509 to nt-76, displayed the characteristics of a CpG island, and overlapped with the promoter region. In conclusion, our data suggest that ZNF703 transcription is regulated by transcription factor Sp1. This finding should facilitate future studies of the mechanism which regulates expression of this important gene.