title: Unique behavior and function of the mitochondrial ribosomal protein S4 (RPS4) in early Dictyostelium development.
abstract: Certain proteins encoded by mitochondrial DNA (mt-DNA), including mt-ribosomal protein S4 (rps4), appear to play important roles in the initiation of cell differentiation. Partial disruption of rps4 in Dictyostelium discoideum Ax-2 cells by means of homologous recombination greatly impairs the progression of differentiation, while the the rps4(OE) cells in which the rps4 mRNA was overexpressed in the extra-mitochondrial cytoplasm exhibit enhanced differentiation (Inazu et al., 1999). We have prepared a specific anti-RPS4 antibody and generated transformants (rps4(AS) cells) by antisense-mediated gene inactivation of rps4. Surprisingly, in the rps4(AS) cells the progress of differentiation was found to be markedly inhibited, suggesting that the antisense rps4 RNA synthesized in the extra-mitochondrial cytoplasm might be as effective as the partial disruption of rps4 gene. Immunostaining of the rps4(OE) cells with the anti-RPS4 antibody demonstrated that the RPS4 protein synthesized in the extra-mitochondrial cytoplasm is capable of moving to the nucleus, as predicted by PSORTII. Taken together with the results obtained using immunostained Ax-2 cells, we propose a possible pathway of RPS4 translocation coupled with differentiation.
authors.affiliation: Department of Developmental Biology and Neurosciences, Graduate School of Life Sciences, Tohoku University, Sendai, Japan.
authors.forename: Koh-Ichi
authors.initials: K
authors.lastname: Hosoya
authors.forename: Aiko
authors.initials: A
authors.lastname: Amagai
authors.forename: Junji
authors.initials: J
authors.lastname: Chida
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Maeda
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000913:Antibodies, Protozoan / Q000276:immunology*; D015153:Blotting, Western; D002454:Cell Differentiation / Q000235:genetics* / Q000502:physiology; D004023:Dictyostelium / Q000235:genetics / Q000254:growth & development* / Q000276:immunology*; D015870:Gene Expression; D020868:Gene Silencing; D007150:Immunohistochemistry; D008969:Molecular Sequence Data; D012269:Ribosomal Proteins / Q000235:genetics* / Q000502:physiology; D016415:Sequence Alignment; D014170:Transformation, Genetic
chemical_list: D000913:Antibodies, Protozoan; D012269:Ribosomal Proteins; C031798:ribosomal protein S4