Abstract
The nucleolar protein gar2, from the fission yeastSchizosaccharomyces pombe, is the functional homolog of NSR1 fromSaccharomyces cerevisiae, and is structurally related to nucleolin from vertebrates. By immunocytochemistry at the electron microscope level, we show that gar2 co-localizes with RNA polymerase I and the gar1 protein along the dense fibrillar component of the nucleolus in a wild-type strain ofS. pombe, suggesting that gar2 is involved in the transcription and/or in the early steps of maturation of the ribosomal RNAs. Since the effects of disruption of thegar2+ gene might also shed light on the role of the gar2 protein, we analyzed the ultrastructure of the nucleolus of agar2-disruption mutant. The nucleolus of thegar2-mutant is dramatically reorganized when compared with that of the wild-typegar2+strain: a truncated protein containing the NH2-terminus of the gar2 protein is accumulated in an unusual nucleolar “dense body”. Our results also suggest that the NH2-terminus might be sufficient for nucleolar localization via interaction with specific nucleolar components and support the hypothesis that gar2 in wild-typeS. pombe interacts with nascent pre-rRNA via its two RNA-binding domains in combination with the glycine/arginine-rich domain. We also report that disruption of thegar2+ gene results in a mutant that is defective in cytokinesis and nuclear division.
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Edited by: S.A. Gerbi
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Léger-Silvestre, I., Gulli, MP., Noaillac-Depeyre, J. et al. Ultrastructural changes in theSchizosaccharomyces pombe nucleolus following the disruption of thegar2+gene, which encodes a nucleolar protein structurally related to nucleolin. Chromosoma 105, 542–552 (1997). https://doi.org/10.1007/BF02510491
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DOI: https://doi.org/10.1007/BF02510491