Requirement of the protein B23 for nucleolar disassembly induced by the FRGY2a family proteins.
In Xenopus somatic cell nuclear cloning, the nucleoli of donor nuclei rapidly and almost completely disappear in egg cytoplasm. We previously showed that the germ cell-specific proteins FRGY2a and FRGY2b were responsible for this unusually drastic nucleolar disassembly. The nucleolar disassembly occurs without inhibition of pre-rRNA transcription, a well known trigger for nucleolar segregation, and the mechanism for the nucleolar disassembly by FRGY2a and FRGY2b remains largely unknown. In this study, we searched for FRGY2a-interacting proteins and investigated the functional consequences of their interactions through a series of experiments. We showed that during the nucleolar disassembly, FRGY2a localized to the nucleoli of isolated nuclei and was capable of disassembling purified nucleoli, suggesting a direct interaction between FRGY2a and nucleolar components. Using a His tag pulldown approach, we identified the abundant and multifunctional nucleolar protein B23 as a potential target of FRGY2a and its related human protein YB1. A specific interaction between FRGY2a/YB1 and B23 was confirmed by co-immunoprecipitation. Finally, B23 knockdown using short interfering RNA and a subsequent add-back experiment confirmed that B23 was necessary for nucleolar disassembly by YB1. We propose that FRGY2a and YB1 disassemble nucleoli by sequestering B23, which is associated with pre-ribosomes and other structurally important nucleolar components.
Gonda
Koichi
K
Stem Cell Institute, Division of Hematology, Oncology and Transplantation, Department of Medicine, University of Minnesota, Minneapolis, Minnesota 55455, USA.
Wudel
Justin
J
Nelson
Dominic
D
Katoku-Kikyo
Nobuko
N
Reed
Peter
P
Tamada
Hiroshi
H
Kikyo
Nobuaki
N
D000818:Animals; D045744:Cell Line, Tumor; D002466:Cell Nucleolus / Q000378:metabolism*; D002467:Cell Nucleus / Q000378:metabolism; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000378:metabolism; D006367:HeLa Cells; D006639:Histidine / Q000737:chemistry; D006801:Humans; D047468:Immunoprecipitation; D013058:Mass Spectrometry; D008854:Microscopy, Electron; D008856:Microscopy, Fluorescence; D009687:Nuclear Proteins / Q000378:metabolism / Q000502:physiology*; D000090243:Nucleophosmin; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D034741:RNA, Small Interfering / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000378:metabolism / Q000502:physiology*; D011994:Recombinant Proteins / Q000737:chemistry; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014157:Transcription Factors / Q000378:metabolism / Q000502:physiology*; D014162:Transfection; D014981:Xenopus; D029867:Xenopus Proteins / Q000378:metabolism / Q000502:physiology*
D018076:DNA, Complementary; D009687:Nuclear Proteins; D034741:RNA, Small Interfering; D016601:RNA-Binding Proteins; D011994:Recombinant Proteins; D014157:Transcription Factors; D029867:Xenopus Proteins; C075593:YBX2 protein, Xenopus; D000090243:Nucleophosmin; D006639:Histidine