title: An RNA-binding protein, RNP-1, protects microtubules from nocodazole and localizes to the leading edge during cytokinesis and cell migration in Dictyostelium cells.
abstract: OBJECTIVE
  RNA-binding proteins are a large group of regulators (800-1000 in humans), some of which play significant roles in mRNA local translation. In this study, we analyzed the functions of the protein RNP-1, which was previously discovered in a genetic selection screen for nocodazole suppression.
  
  
  METHODS
  The growth rates and the microtubule networks of Dictyostelium cells were assessed with or without nocodazole (10 μmol/L) in suspension culture. Fluorescent images of RNP-1-GFP and RFP-tubulin were captured when cells were undergoing cytokinesis, then the GFP signal intensity and distance to the nearest centrosome were analyzed by using a computer program written in Matlab®. The RNP-1-GFP-expresseding cells were polarized, and the time-lapse images of cells were captured when cells were chemotaxing to a cAMP source.
  
  
  RESULTS
  Over-expression of RNP-1 rescued the growth defects caused by the microtubule-destabilizing agent nocodazole. Over-expression of RNP-1 protected microtubules from nocodazole treatment. In cells undergoing cytokinesis, the RNP-1 protein was localized to the polar regions of the cell cortex, and protein levels decreased proportionally as the power of the distance from the cell cortex to the nearest centrosome. In chemotactic cells, the RNP-1 protein localized to the leading edge of moving cells. Sequence analysis revealed that RNP-1 has two RNA-binding domains and is related to cytosolic poly(A)-binding proteins (PABPCs) in humans.
  
  
  CONCLUSIONS
  RNP-1 has roles in protecting microtubules and in directing cortical movement during cytokinesis and cell migration in Dictyostelium cells. The sequence similarity of RNP-1 to human PABPCs suggests that PABPCs may have similar functions in mammalian cells, perhaps in regulating microtubule dynamics and functions during cortical movement in cytokinesis and cell migration.
authors: Department of Biomedical Sciences, School of Human and Health Services, Missouri State University, Springfield, MO 65897, USA.
authors: Thu
authors: T
authors: Ngo
authors: Department of Geography, Geology, and Planning, Missouri State University, Springfield, MO 65897, USA.
authors: Xin
authors: X
authors: Miao
authors: Department of Cell Biology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
authors: Douglas N
authors: DN
authors: Robinson
authors: Department of Biomedical Sciences, School of Human and Health Services, Missouri State University, Springfield, MO 65897, USA.|Department of Biology, Denison University, Granvillle, OH 43023, USA.
authors: Qiong-Qiong
authors: QQ
authors: Zhou
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology*; D002465:Cell Movement; D048749:Cytokinesis; D004023:Dictyostelium / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D008870:Microtubules / Q000187:drug effects* / Q000648:ultrastructure; D015739:Nocodazole / Q000494:pharmacology*; D015800:Protozoan Proteins / Q000378:metabolism*; D000067776:RNA Recognition Motif Proteins / Q000378:metabolism*
chemical_list: D000970:Antineoplastic Agents; D015800:Protozoan Proteins; D000067776:RNA Recognition Motif Proteins; D015739:Nocodazole