Fal1p is an essential DEAD-box protein involved in 40S-ribosomal-subunit biogenesis in Saccharomyces cerevisiae.
A previously uncharacterized Saccharomyces cerevisiae gene, FAL1, was found by sequence comparison as a homolog of the eukaryotic translation initiation factor 4A (eIF4A). Fal1p has 55% identity and 73% similarity on the amino acid level to yeast eIF4A, the prototype of ATP-dependent RNA helicases of the DEAD-box protein family. Although clearly grouped in the eIF4A subfamily, the essential Fal1p displays a different subcellular function and localization. An HA epitope-tagged Fal1p is localized predominantly in the nucleolus. Polysome analyses in a temperature-sensitive fal1-1 mutant and a Fal1p-depleted strain reveal a decrease in the number of 40S ribosomal subunits. Furthermore, these strains are hypersensitive to the aminoglycoside antibiotics paromomycin and neomycin. Pulse-chase labeling of pre-rRNA and steady-state-level analysis of pre-rRNAs and mature rRNAs by Northern hybridization and primer extension in the Fal1p-depleted strain show that Fal1p is required for pre-rRNA processing at sites A0, A1, and A2. Consequently, depletion of Fal1p leads to decreased 18S rRNA levels and to an overall deficit in 40S ribosomal subunits. Together, these results implicate Fal1p in the 18S rRNA maturation pathway rather than in translation initiation.
Kressler
D
D
Département de Biochimie Médicale, Centre Médical Universitaire, Université de Genève, Switzerland.
de la Cruz
J
J
Rojo
M
M
Linder
P
P
D000595:Amino Acid Sequence; D000617:Aminoglycosides; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001483:Base Sequence; D002466:Cell Nucleolus / Q000378:metabolism; D017931:DNA Primers / Q000235:genetics; D004352:Drug Resistance, Microbial; D039601:Eukaryotic Initiation Factor-4A; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D005800:Genes, Fungal; D008969:Molecular Sequence Data; D009154:Mutation; D010448:Peptide Initiation Factors / Q000235:genetics; D016133:Polymerase Chain Reaction; D012322:RNA Precursors / Q000378:metabolism; D012323:RNA Processing, Post-Transcriptional; D012331:RNA, Fungal / Q000378:metabolism; D012337:RNA, Ribosomal, 18S / Q000378:metabolism; D016601:RNA-Binding Proteins; D012270:Ribosomes / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins; D017386:Sequence Homology, Amino Acid
D000617:Aminoglycosides; D000900:Anti-Bacterial Agents; D017931:DNA Primers; C109242:FAL1 protein, S cerevisiae; D005656:Fungal Proteins; D010448:Peptide Initiation Factors; D012322:RNA Precursors; D012331:RNA, Fungal; D012337:RNA, Ribosomal, 18S; D016601:RNA-Binding Proteins; D029701:Saccharomyces cerevisiae Proteins; D039601:Eukaryotic Initiation Factor-4A