title: The PcG protein HPC2 inhibits RBP-J-mediated transcription by interacting with LIM protein KyoT2.
abstract: The DNA-binding protein recombination signal-binding protein-Jk (RBP-J) plays a key role in transcriptional regulation by targeting the intracellular domain of Notch (NIC) and the Epstein-Barr virus nuclear antigen 2 (EBNA2) to specific promoters. In the absence of the Notch signaling, RBP-J acts as a transcriptional suppressor through recruiting co-suppressors such as histone deacetylase (HDAC). KyoT2 is a LIM domain protein that suppresses the RBP-J-mediated transcriptional activation. In the current study, we show that the polycomb group (PcG) protein HPC2, which functions as a transcriptional suppressor, is a candidate of KyoT2-binding proteins. To confirm the physical and functional interaction between KyoT2 and HPC2, we carried out yeast two-hybrid, GST-pull down, co-immunoprecipitation, as well as mammalian two-hybrid assays. Our results showed HPC2 and KyoT2 interacted both in vitro and in vivo, probably through the C-terminal fragment of HPC2 and LIM domains of KyoT2. In addition, we also found that overexpression of HPC2, not only inhibited transactivation of a RBP-J-dependent promoter by NIC, but also transactivation by RBP-J-VP16, a constitutively active form of RBP-J. Taken together, our results suggested that KyoT2 might inhibit the RBP-J-mediated transactivation through NIC by recruiting co-suppressors such as HPC2.
authors.affiliation: State Key Laboratory of GI Cancer Biology, Department of Medical Genetics and Developmental Biology, Fourth Military Medical University, Chang-Le Xi Street, Xi'an 710032, Shaanxi Province, PR China.
authors.forename: Hongyan
authors.initials: H
authors.lastname: Qin
authors.forename: Dewei
authors.initials: D
authors.lastname: Du
authors.forename: Yangting
authors.initials: Y
authors.lastname: Zhu
authors.forename: Junfeng
authors.initials: J
authors.lastname: Li
authors.forename: Lei
authors.initials: L
authors.lastname: Feng
authors.forename: Yingmin
authors.initials: Y
authors.lastname: Liang
authors.forename: Hua
authors.initials: H
authors.lastname: Han
mesh_terms: D002460:Cell Line; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D006801:Humans; D051819:Immunoglobulin J Recombination Signal Sequence-Binding Protein; D047468:Immunoprecipitation; D008025:Ligases; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D046912:Multiprotein Complexes / Q000737:chemistry / Q000378:metabolism; D009124:Muscle Proteins / Q000235:genetics / Q000378:metabolism*; D009687:Nuclear Proteins / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D063146:Polycomb-Group Proteins; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding; D051880:Receptors, Notch; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic; D015533:Transcriptional Activation / Q000235:genetics; D044767:Ubiquitin-Protein Ligases
chemical_list: D004268:DNA-Binding Proteins; D051819:Immunoglobulin J Recombination Signal Sequence-Binding Protein; D008565:Membrane Proteins; D046912:Multiprotein Complexes; D009124:Muscle Proteins; D009687:Nuclear Proteins; D063146:Polycomb-Group Proteins; C497570:RBPJ protein, human; D051880:Receptors, Notch; D012097:Repressor Proteins; D044767:Ubiquitin-Protein Ligases; D008025:Ligases; C570427:CBX4 protein, human