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Original Article |
Correspondence to: Sunghoon Kim, National Creative Research Initiatives Center for ARS Network, Sung Kyun Kwan University, 300 Chunchundong, Jangangu, Suwon, Kyunggido 440-746, Korea. Tel:82-331-290-5681 Fax:82-331-290-5682 E-mail:shkim{at}yurim.skku.ac.kr.
Human aminoacyltRNA synthetases (ARSs) are normally located in cytoplasm and are involved in protein synthesis. In the present work, we found that human methionyltRNA synthetase (MRS) was translocated to nucleolus in proliferative cells, but disappeared in quiescent cells. The nucleolar localization of MRS was triggered by various growth factors such as insulin, PDGF, and EGF. The presence of MRS in nucleoli depended on the integrity of RNA and the activity of RNA polymerase I in the nucleolus. The ribosomal RNA synthesis was specifically decreased by the treatment of anti-MRS antibody as determined by nuclear run-on assay and immunostaining with anti-Br antibody after incorporating Br-UTP into nascent RNA. Thus, human MRS plays a role in the biogenesis of rRNA in nucleoli, while it is catalytically involved in protein synthesis in cytoplasm.
Key Words: methionyltRNA synthetase, nucleoli, growth signal, ribosomal RNA synthesis, RNA polymerase I
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