Characterization of nuclear polyadenylated RNA-binding proteins in Saccharomyces cerevisiae.
To study the functions of heterogeneous nuclear ribonucleoproteins (hnRNPs), we have characterized nuclear polyadenylated RNA-binding (Nab) proteins from Saccharomyces cerevisiae. Nab1p, Nab2p, and Nab3p were isolated by a method which uses UV light to cross-link proteins directly bound to poly(A)+ RNA in vivo. We have previously characterized Nab2p, and demonstrated that it is structurally related to human hnRNPs. Here we report that Nab1p is identical to the Np13p/Nop3p protein recently implicated in both nucleocytoplasmic protein shuttling and pre-rRNA processing, and characterize a new nuclear polyadenylated RNA-binding protein, Nab3p. The intranuclear distributions of the Nab proteins were analyzed by three-dimensional immunofluorescence optical microscopy. All three Nab proteins are predominantly localized within the nucleoplasm in a pattern similar to the distribution of hnRNPs in human cells. The NAB3 gene is essential for cell viability and encodes an acidic ribonucleoprotein. Loss of Nab3p by growth of a GAL::nab3 mutant strain in glucose results in a decrease in the amount of mature ACT1, CYH2, and TPI1 mRNAs, a concomitant accumulation of unspliced ACT1 pre-mRNA, and an increase in the ratio of unspliced CYH2 pre-mRNA to mRNA. These results suggest that the Nab proteins may be required for packaging pre-mRNAs into ribonucleoprotein structures amenable to efficient nuclear RNA processing.
Wilson
S M
SM
Department of Immunology and Medical Microbiology, University of Florida, College of Medicine, Gainesville 32610-0266.
Datar
K V
KV
Paddy
M R
MR
Swedlow
J R
JR
Swanson
M S
MS
D000595:Amino Acid Sequence; D001483:Base Sequence; D002455:Cell Division; D002467:Cell Nucleus / Q000737:chemistry; D002470:Cell Survival; D005656:Fungal Proteins / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism; D005800:Genes, Fungal; D034441:Heterogeneous-Nuclear Ribonucleoproteins; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism; D029543:Nucleocytoplasmic Transport Proteins; D012322:RNA Precursors / Q000378:metabolism; D012323:RNA Processing, Post-Transcriptional; D012331:RNA, Fungal / Q000378:metabolism; D012332:RNA, Heterogeneous Nuclear / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism; D012261:Ribonucleoproteins / Q000737:chemistry; D012441:Saccharomyces cerevisiae / Q000737:chemistry* / Q000235:genetics / Q000254:growth & development; D029701:Saccharomyces cerevisiae Proteins
D005656:Fungal Proteins; D034441:Heterogeneous-Nuclear Ribonucleoproteins; C080773:NAB2 protein, S cerevisiae; C090564:NAB3 protein, S cerevisiae; C077734:NPL3 protein, S cerevisiae; D009687:Nuclear Proteins; D029543:Nucleocytoplasmic Transport Proteins; D012322:RNA Precursors; D012331:RNA, Fungal; D012332:RNA, Heterogeneous Nuclear; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D012261:Ribonucleoproteins; D029701:Saccharomyces cerevisiae Proteins