Abstract
NOG1 is a P-loop GTPase that belongs to the Obg-Hflx super family and is conserved among archaea and eukaryotes. In yeast, and mouse, NOG1 has been shown to be essential for cell viability and functionally linked to 60S ribosomal maturation. Arabidopsis thaliana contains two NOG1 genes (NOG1-1 and NOG1-2), but only NOG1-1 is constitutively expressed in all developmental stages of plant. The NOG1-1 was accumulated in nucleolus and nucleoplasm. Fractionation analysis suggested that the NOG1-1 was present in the preribosomal fractions. Moreover, FRAP analysis revealed that the distribution of NOG1-1 protein between nucleolus and nucleoplasm was sensitive to transcription and translation inhibitors, and carbon and nitrate starvation, suggesting that NOG1-1 plays an essential role in early and intermediate steps of ribosomal biogenesis. Furthermore, The NOG1-1 protein disappeared in pre-metaphase, and is rapidly re-accumulated in peripheral chromosomal region in early anaphase. NOG1-1may also play another important role in nucleolus dynamics.
