Zfp296 is a novel Klf4-interacting protein and functions as a negative regulator.

Pluripotency and self-renewing ability of embryonic stem (ES) cells are regulated by several transcription factors, including Oct3/4, Sox2, Kruppel-like factor 4 (Klf4), and c-Myc. These transcription factors reprogram somatic cells into induced pluripotent stem (iPS) cells. Zinc finger protein (Zfp) 296 has been reported to enhance iPS cell formation. Here we found that Zfp296 interacts with Klf4. A maltose-binding protein pull-down assay demonstrated that Klf4 binds to the Zfp296 158-483 amino acid region, and that Zfp296 binds to the Klf4 DNA-binding domain (DBD). A quantitative reverse transcription-polymerase chain reaction analysis revealed that expression of Zfp296 and Klf4 decreased during differentiation of E14 and ZHBTc4 ES cells. We also found that green fluorescent protein-labeled Zfp296 and Klf4 were localized to the nucleus. Because Zfp296 bound to the Klf4 DBD, we next examined the influence of Zfp296 on Klf4 DNA-binding activity. A biotin DNA pull-down assay showed that Klf4 binds to the Lefty1 promoter region, and that binding activity was sustained even in the presence of Zfp296. In contrast, a reporter assay showed that the Lefty1 promoter was activated by Klf4, and that the enhanced activity was repressed by Zfp296. These findings suggest that Zfp296 is a functional regulator of Klf4 in ES cells.