title: A new role of GCN2 in the nucleolus.
abstract: General control nonderepressible 2 (GCN2) is activated by the accumulation of uncharged tRNA in response to amino acid shortage and regulates amino acid starvation response in the cytosol. Here we report the nucleolar localization of GCN2 and the association between GCN2 and small RNA transcripts. Immunofluorescence analysis revealed that GCN2 was constitutively localized to the nucleolus or recruited to the nucleolus by amino acid starvation stress. The nucleolus is the largest structure in the nucleus, where it primarily serves as the site of ribosome and RNA synthesis in addition to acting as a stress sensor through the regulation of p53 function. We found that siRNA-mediated depletion of GCN2 increases small RNA transcripts such as tRNA and 5S rRNA, and induces the p53 pathway activation. Derepression of these transcripts and p53 pathway activation by GCN2 depletion was restored by depletion of B-related factor 1 (BRF1), a primary subunit of RNA polymerase III (pol III) components. These data suggest that the excess amount of small RNA transcripts following GCN2 depletion was responsible for the p53 activation. Our findings reveal a role of GCN2 in the nucleolus that is involved in the expression of small RNA transcripts and serves as alternative stress-sensing machinery for nutrient deficiency. Thus, GCN2 may play pivotal roles in multiple protein translation checkpoints in both the nucleolus and cytosol.
authors.affiliation: Oncology Drug Discovery Unit, Takeda Pharmaceutical Company Limited, Kanagawa 251-8555, Japan. Electronic address: akito.nakamura@takeda.com.
authors.forename: Akito
authors.initials: A
authors.lastname: Nakamura
authors.affiliation: Oncology Drug Discovery Unit, Takeda Pharmaceutical Company Limited, Kanagawa 251-8555, Japan. Electronic address: hiromichi.kimura@astellas.com.
authors.forename: Hiromichi
authors.initials: H
authors.lastname: Kimura
mesh_terms: D000072283:A549 Cells; D015153:Blotting, Western; D045744:Cell Line, Tumor; D002466:Cell Nucleolus / Q000378:metabolism*; D015972:Gene Expression Regulation, Neoplastic; D006367:HeLa Cells; D006801:Humans; D018613:Microscopy, Confocal; D017346:Protein Serine-Threonine Kinases / Q000235:genetics* / Q000378:metabolism; D034622:RNA Interference; D012341:RNA, Ribosomal, 5S / Q000235:genetics*; D012343:RNA, Transfer / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000235:genetics; D035381:TATA-Binding Protein Associated Factors / Q000235:genetics / Q000378:metabolism; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism
chemical_list: C441028:BRF1 protein, human; D012341:RNA, Ribosomal, 5S; D035381:TATA-Binding Protein Associated Factors; D016159:Tumor Suppressor Protein p53; D012343:RNA, Transfer; C529271:EIF2AK4 protein, human; D017346:Protein Serine-Threonine Kinases
keywords: Amino acid starvation; GCN2; Nucleolus; RNA polymerase III; p53