Nspc1 is an identified transcription repressor. However, transiently up-regulated or down-regulated Nspc1 in P19 embryonal carcinoma cells affects expression levels of Oct4, Sox2 and Nanog in a positive correlation. Luciferase activity assays verified that Nspc1 regulates the Oct4 promoter in a dose dependent manner. ChIP assay shows that Nspc1 activates Oct4 by directly binding to the (-1021 to 784) region of Oct4 promoter. Dominant negative analysis indicated the activation is dependent on the retinoid acid response element (RARE). We demonstrated Nspc1 has a positive role in maintaining the pluripotency of P19 cells by directly regulating Oct4. (C) 2013 Elsevier Inc. All rights reserved.