The Arabidopsis CBP20 targets the cap-binding complex to the nucleus, and is stabilized by CBP80.
The cap-binding protein complex (CBC) binds to the caps of all RNA polymerase II transcripts, and plays an important role in RNA metabolism. We characterized interactions, localization and nuclear-cytoplasmic transport of two subunits of the Arabidopsis thaliana cap-binding protein complex (AtCBC): AtCBP20 and AtCBP80. Using CFP/YFP-tagged proteins, we show that transport of AtCBC from the cytoplasm to the nucleus in the plant cell is different from that described in other eukaryotic cells. We show that the smaller subunit of the complex, AtCBP20, plays a crucial role in the nuclear import of AtCBC. The C-terminal part of AtCBP20 contains two functionally independent nuclear localization signals (NLSs). At least one of these two NLSs is required for the import of CBC into the plant nucleus. The interaction between the A. thaliana CBP20 and CBP80 was also analyzed in detail, using the yeast two-hybrid system and fluorescence resonance energy transfer (FRET) assays. The N-terminal part of AtCBP20 is essential for interaction with AtCBP80. Furthermore, AtCBP80 is important for the protein stability of the smaller subunit of CBC. Based on these data, we propose a model for the nuclear-cytoplasmic trafficking of the CBC complex in plants.
Kierzkowski
Daniel
D
Department of Molecular and Cellular Biology, Faculty of Biology, Adam Mickiewicz University, Umultowska, Poland.
Kmieciak
Maciej
M
Piontek
Paulina
P
Wojtaszek
Przemyslaw
P
Szweykowska-Kulinska
Zofia
Z
Jarmolowski
Artur
A
D021581:Active Transport, Cell Nucleus; D017360:Arabidopsis / Q000235:genetics* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002467:Cell Nucleus / Q000378:metabolism; D031541:Fluorescence Resonance Energy Transfer; D019913:Nuclear Localization Signals / Q000235:genetics / Q000378:metabolism; D021122:Protein Subunits / Q000235:genetics / Q000378:metabolism; D021381:Protein Transport; D039381:RNA Cap-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D018749:RNA, Plant / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D020798:Two-Hybrid System Techniques
D029681:Arabidopsis Proteins; D019913:Nuclear Localization Signals; D021122:Protein Subunits; D039381:RNA Cap-Binding Proteins; D018749:RNA, Plant; D016601:RNA-Binding Proteins; C454128:CBP20 protein, Arabidopsis; C435105:At2g13540 protein, Arabidopsis