Mutations in nucleolar proteins lead to nucleolar accumulation of polyA+ RNA in Saccharomyces cerevisiae.
Synthesis of mRNA and rRNA occur in the chromatin-rich nucleoplasm and the nucleolus, respectively. Nevertheless, we here report that a Saccharomyces cerevisiae gene, MTR3, previously implicated in mRNA transport, codes for a novel essential 28-kDa nucleolar protein. Moreover, in mtr3-1 the accumulated polyA+ RNA actually colocalizes with nucleolar antigens, the nucleolus becomes somewhat disorganized, and rRNA synthesis and processing are inhibited. A strain with a ts conditional mutation in RNA polymerase I also shows nucleolar accumulation of polyA+ RNA, whereas strains with mutations in the nucleolar protein Nop1p do not. Thus, in several mutant backgrounds, when mRNA cannot be exported i concentrates in the nucleolus. mRNA may normally encounter nucleolar components before export and proteins such as Mtr3p may be critical for export of both mRNA and ribosomal subunits.
Kadowaki
T
T
Department of Genetics, Harvard Medical School, Boston, Massachusetts 02115, USA.
Schneiter
R
R
Hitomi
M
M
Tartakoff
A M
AM
D000595:Amino Acid Sequence; D001483:Base Sequence; D001692:Biological Transport; D002466:Cell Nucleolus / Q000378:metabolism*; D003001:Cloning, Molecular; D005092:Exonucleases; D063326:Exosome Multienzyme Ribonuclease Complex; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D005800:Genes, Fungal; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D012319:RNA Polymerase II / Q000378:metabolism; D012331:RNA, Fungal / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism*; D012335:RNA, Ribosomal / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins
D005656:Fungal Proteins; D009687:Nuclear Proteins; D012331:RNA, Fungal; D012333:RNA, Messenger; D012335:RNA, Ribosomal; D029701:Saccharomyces cerevisiae Proteins; D012319:RNA Polymerase II; D005092:Exonucleases; D063326:Exosome Multienzyme Ribonuclease Complex; C097433:MTR3 protein, S cerevisiae