Résumé
We report the identification of a novel nucleolar protein from fission yeast, p17nhp2, which is homologous to the recently identified Nhp2p core component of H+ACA snoRNPs in Saccharomyces cerevisiae. We show that the fission yeast p17nhp2 localizes to the nucleolus in live S. cerevisiae or Schizosaccharomyces pombe cells and is functionally conserved since the fission yeast gene can complement a deletion of the NHP2 gene in budding yeast. Analysis of p17nhp2 during the mitotic cell cycles of living fission and budding yeast cells shows that this protein, and by implication H+ACA snoRNPs, remains localized with nucleolar material during mitosis, although the gross organization of partitioning of p17nhp2 during anaphase is different in a comparison of the two yeasts. During anaphase in S. pombe p17nhp2 trails segregating chromatin, while in S. cerevisiae the protein segregates alongside bulk chromatin. The pattern of segregation comparing haploid and diploid S. cerevisiae cells suggests that p17nhp2 is closely associated with the rDNA during nuclear division.