A novel genetic screen for snRNP assembly factors in yeast identifies a conserved protein, Sad1p, also required for pre-mRNA splicing.
Mol Cell Biol
; 19(3): 2008-20, 1999 Mar.
Article
en En
| MEDLINE
| ID: mdl-10022888
The assembly pathway of spliceosomal snRNPs in yeast is poorly understood. We devised a screen to identify mutations blocking the assembly of newly synthesized U4 snRNA into a functional snRNP. Fifteen mutant strains failing either to accumulate the newly synthesized U4 snRNA or to assemble a U4/U6 particle were identified and categorized into 13 complementation groups. Thirteen previously identified splicing-defective prp mutants were also assayed for U4 snRNP assembly defects. Mutations in the U4/U6 snRNP components Prp3p, Prp4p, and Prp24p led to disassembly of the U4/U6 snRNP particle and degradation of the U6 snRNA, while prp17-1 and prp19-1 strains accumulated free U4 and U6 snRNA. A detailed analysis of a newly identified mutant, the sad1-1 mutant, is presented. In addition to having the snRNP assembly defect, the sad1-1 mutant is severely impaired in splicing at the restrictive temperature: the RP29 pre-mRNA strongly accumulates and splicing-dependent production of beta-galactosidase from reporter constructs is abolished, while extracts prepared from sad1-1 strains fail to splice pre-mRNA substrates in vitro. The sad1-1 mutant is the only splicing-defective mutant analyzed whose mutation preferentially affects assembly of newly synthesized U4 snRNA into the U4/U6 particle. SAD1 encodes a novel protein of 52 kDa which is essential for cell viability. Sad1p localizes to the nucleus and is not stably associated with any of the U snRNAs. Sad1p contains a putative zinc finger and is phylogenetically highly conserved, with homologues identified in human, Caenorhabditis elegans, Arabidospis, and Drosophila.
Texto completo:
1
Colección:
01-internacional
Base de datos:
MEDLINE
Asunto principal:
Proteínas Quinasas
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Saccharomyces cerevisiae
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ARN de Hongos
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Proteínas Fúngicas
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Precursores del ARN
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Empalme del ARN
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Ribonucleoproteína Nuclear Pequeña U4-U6
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Proteínas Serina-Treonina Quinasas
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Proteínas de Ciclo Celular
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Proteínas de Saccharomyces cerevisiae
Tipo de estudio:
Prognostic_studies
Límite:
Animals
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Humans
Idioma:
En
Revista:
Mol Cell Biol
Año:
1999
Tipo del documento:
Article
País de afiliación:
Alemania
Pais de publicación:
Estados Unidos