title: DPF2 regulates OCT4 protein level and nuclear distribution.
abstract: The amount of transcription factor OCT4 is strictly regulated. A tight regulation of OCT4 levels is crucial for mammalian embryonic development and oncogenesis. However, the mechanisms underlying regulation of OCT4 protein expression and nuclear distribution are largely unknown. Here, we report that DPF2, a plant homeodomain (PHD) finger protein, is upregulated during H9 cell differentiation induced by retinoic acid. Endogenous interaction between DPF2 and OCT4 in P19 cells was revealed by an immunoprecipitation assay. GST-pull down assay proved that OCT4 protein in H9 cells and recombinant OCT4 can precipitate with DPF2 in vitro. In vitro ubiquitination assay demonstrated DPF2 might serve as an E3 ligase. Knock down of dpf2 using siRNA increased OCT4 protein level and stability in P19 cells. DPF2 siRNAs also up-regulates OCT4 but not NANOG in H9 cells. However, RA fails to downregulates OCT4 protein level in cells infected by lenitviruses containing DPF2 siRNA. Moreover, overexpression of both DPF2 and OCT4 in 293 cells proved the DPF2-OCT4 interaction. DPF2 but not PHD2 mutant DPF2 enhanced ubiquitination and degradation of OCT4 in 293 cells co-expressed DPF2 and OCT4. Both wild type DPF2 and PHD2 mutant DPF2 redistributes nuclear OCT4 without affecting DPF2-OCT4 interaction. Further analysis indicated that DPF2 decreases monomeric and mono-ubiquitinated OCT4, assembles poly-ubiquitin chains on OCT4 mainly through Ub-K48 linkage. These findings contribute to an understanding of how OCT4 protein level and nuclear distribution is regulated by its associated protein.
authors.affiliation: Department of Histology and Embryology, Institute of Stem Cell and Tissue Engineering, School of Basic Medical Sciences, Anhui Medical University, Hefei, Anhui 230032 China; Center for Biomedical Engineering and Technology (BioMET), University of Maryland, Baltimore, MD 21201 USA. Electronic address: chaol1974@ahmu.edu.cn.
authors.forename: Chao
authors.initials: C
authors.lastname: Liu
authors.affiliation: Department of Histology and Embryology, Institute of Stem Cell and Tissue Engineering, School of Basic Medical Sciences, Anhui Medical University, Hefei, Anhui 230032 China.
authors.forename: Dijuan
authors.initials: D
authors.lastname: Zhang
authors.affiliation: School of Basic Medical Sciences, Institute of Biopharmaceuticals, Anhui Medical University, Hefei, Anhui 230032 China.
authors.forename: Yuxian
authors.initials: Y
authors.lastname: Shen
authors.affiliation: School of Basic Medical Sciences, Institute of Biopharmaceuticals, Anhui Medical University, Hefei, Anhui 230032 China.
authors.forename: Xiaofang
authors.initials: X
authors.lastname: Tao
authors.affiliation: Institute of Clinical Pharmacology, Anhui Medical University, Hefei, Anhui 230032, China.
authors.forename: Lihua
authors.initials: L
authors.lastname: Liu
authors.affiliation: Center for Biomedical Engineering and Technology (BioMET), University of Maryland, Baltimore, MD 21201 USA.
authors.forename: Yongwang
authors.initials: Y
authors.lastname: Zhong
authors.affiliation: Center for Biomedical Engineering and Technology (BioMET), University of Maryland, Baltimore, MD 21201 USA. Electronic address: sfang@umaryland.edu.
authors.forename: Shengyun
authors.initials: S
authors.lastname: Fang
mesh_terms: D002454:Cell Differentiation / Q000187:drug effects; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000502:physiology*; D006801:Humans; D050814:Octamer Transcription Factor-3 / Q000378:metabolism*; D011485:Protein Binding; D014157:Transcription Factors; D014212:Tretinoin / Q000494:pharmacology; D054875:Ubiquitination
chemical_list: D004268:DNA-Binding Proteins; C113581:DPF2 protein, human; D050814:Octamer Transcription Factor-3; C494173:POU5F1 protein, human; D014157:Transcription Factors; D014212:Tretinoin
keywords: DPF2; E3; OCT4; PHD finger; Ubiquitination