Zinc Finger and X-Linked Factor (ZFX) Binds to Human SET Transcript 2 Promoter and Transactivates SET Expression

Abstract

SET protein carries out multiple functions including those for protein phosphatase 2A (PP2A) inhibition, histone modification, DNA repair and gene regulation. SET overexpression has been detected in brain neurons of Alzheimer's disease patients, follicle theca cells of Polycystic Ovary Syndrome (PCOS) patients, and ovarian cancer cells, indicating that SET may play a pathological role for these disorders. SET transcript 2, produced by a specific promoter, represents a major transcript variant in different cell types. In this study, we characterized the transcriptional activation of human SET transcript 2 promoter in HeLa cells. Promoter deletion experiments and co-transfection assays indicated that ZFX, the Zinc finger and X-linked transcription factor, was able to transactivate the SET promoter. A proximal promoter region containing four ZFX-binding sites was found to be critical for the ZFX-mediated transactivation. Mutagenesis study indicated that the site located closest to the transcription start site accounted for most of the ZFX-mediated transactivity. Manipulation of ZFX levels by overexpression or siRNA knockdown confirmed the significance and specificity of the ZFX-mediated SET promoter activation. Chromatin immunoprecipitation results verified the binding of ZFX to its cognate site in the SET promoter. These findings have led to identification of ZFX as an upstream factor regulating SET gene expression. More studies are required to define the in vivo significance of this mechanism, and specifically, its implication for several benign and malignant diseases related to SET dysregulation.

A comprehensive and perspective view of oncoprotein SET in cancer

“…that are critical for SET-β transactivation in both HEK293 and HeLa cells. 65 Multiple Sp1 binding sites are found in both SET-α and SET-β promoter regions, but their effects on each isoform transcription are different. In HEK 293, HeLa, AML, HL-60, and HEL cells Sp1 positively contributes to SET-α gene transcription in vivo while Sp1 knockdown leads to reduction in SET-α mRNA level, whereas Sp1 deficiency has no effect on SET-β transcription.…”

“…These TFs are usually overexpressed in cancer cells, thereby enhancing the transcription of SET. Siliang et al found that there are 4 zinc finger and X‐linked factor (ZFX) binding sites in the proximal promoter region that are critical for SET‐β transactivation in both HEK293 and HeLa cells . Multiple Sp1 binding sites are found in both SET‐α and SET‐β promoter regions, but their effects on each isoform transcription are different.…”