The Nop60B gene of Drosophila encodes an essential nucleolar protein that functions in yeast.
The Cbf5 protein of Saccharomyces cerevisiae was originally identified as a low-affinity centromeric DNA-binding protein, and chf5 mutants have a defect in rRNA synthesis. A closely related protein from mammals, NAP57, is a nucleolar protein that coimmunoprecipitates with the nucleolar phosphoprotein Nopp140. To study the function of this protein family in a higher eukaryote that is amenable to genetic approaches, the gene encoding a Drosophila melanogaster homolog, Nop60B, was identified. The predicted Drosophila protein shares a high degree of sequence identity over a 380-residue region with both the mammalian and yeast proteins, and shares several conserved motifs with the prokaryotic tRNA pseudouridine 55 synthases. Nop60B RNA is found at high levels in nurse cells and in the oocyte, and is present throughout development. Nop60B protein is localized primarily to the nucleolus of interphase cells, and is absent from the chromosomes during mitosis. Nop60B mutants were generated and shown to be homozygous lethal. The Drosophila gene can rescue the lethal phenotype of yeast chf5 mutations, showing that the function of this protein has been conserved from yeast to Drosophila.
Phillips
B
B
Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara 93106, USA.
Billin
A N
AN
Cadwell
C
C
Buchholz
R
R
Erickson
C
C
Merriam
J R
JR
Carbon
J
J
Poole
S J
SJ
D000595:Amino Acid Sequence; D000818:Animals; D002451:Cell Compartmentation; D002466:Cell Nucleolus / Q000737:chemistry*; D004330:Drosophila / Q000235:genetics*; D029721:Drosophila Proteins; D015870:Gene Expression; D020043:Genes, Essential; D017344:Genes, Insect; D005816:Genetic Complementation Test; D006836:Hydro-Lyases; D019753:Intramolecular Lyases / Q000235:genetics; D019751:Intramolecular Transferases; D008869:Microtubule-Associated Proteins / Q000235:genetics; D008969:Molecular Sequence Data; D005810:Multigene Family; D009687:Nuclear Proteins / Q000235:genetics*; D016601:RNA-Binding Proteins / Q000235:genetics; D017411:Ribonucleoproteins, Small Nuclear; D029701:Saccharomyces cerevisiae Proteins; D017386:Sequence Homology, Amino Acid; D014018:Tissue Distribution; D015003:Yeasts / Q000235:genetics
D029721:Drosophila Proteins; D008869:Microtubule-Associated Proteins; C107170:NAP57; D009687:Nuclear Proteins; D016601:RNA-Binding Proteins; D017411:Ribonucleoproteins, Small Nuclear; D029701:Saccharomyces cerevisiae Proteins; D006836:Hydro-Lyases; C082278:CBF5 protein, S cerevisiae; C119240:Nop60B protein, Drosophila; D019751:Intramolecular Transferases; C096995:pseudouridine synthases; D019753:Intramolecular Lyases