Dataset Information

Targeting of U4/U6 small nuclear RNP assembly factor SART3/p110 to Cajal bodies.

ABSTRACT: The spliceosomal small nuclear RNAs (snRNAs) are distributed throughout the nucleoplasm and concentrated in nuclear inclusions termed Cajal bodies (CBs). A role for CBs in the metabolism of snRNPs has been proposed but is not well understood. The SART3/p110 protein interacts transiently with the U6 and U4/U6 snRNPs and promotes the reassembly of U4/U6 snRNPs after splicing in vitro. Here we report that SART3/p110 is enriched in CBs but not in gems or residual CBs lacking coilin. The U6 snRNP Sm-like (LSm) proteins, also involved in U4/U6 snRNP assembly, were localized to CBs as well. The levels of SART3/p110 and LSm proteins in CBs were reduced upon treatment with the transcription inhibitor alpha-amanitin, suggesting that CB localization reflects active processes dependent on transcription/splicing. The NH2-terminal HAT domain of SART3/p110 was necessary and sufficient for specific protein targeting to CBs. Overexpression of truncation mutants containing the HAT domain had dominant negative effects on U6 snRNP localization to CBs, indicating that endogenous SART3/p110 plays a role in targeting the U6 snRNP to CBs. We propose that U4 and U6 snRNPs accumulate in CBs for the purpose of assembly into U4/U6 snRNPs by SART3/p110.

SUBMITTER: Stanek D

PROVIDER: S-EPMC2173746 | biostudies-literature | 2003 Feb

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

Targeting of U4/U6 small nuclear RNP assembly factor SART3/p110 to Cajal bodies.

Stanĕk David D Rader Stephen D SD Klingauf Mirko M Neugebauer Karla M KM

The Journal of cell biology 20030210 4

The spliceosomal small nuclear RNAs (snRNAs) are distributed throughout the nucleoplasm and concentrated in nuclear inclusions termed Cajal bodies (CBs). A role for CBs in the metabolism of snRNPs has been proposed but is not well understood. The SART3/p110 protein interacts transiently with the U6 and U4/U6 snRNPs and promotes the reassembly of U4/U6 snRNPs after splicing in vitro. Here we report that SART3/p110 is enriched in CBs but not in gems or residual CBs lacking coilin. The U6 snRNP Sm- ...[more]

PMID: 12578909

Similar Datasets

Project description:The rnp-4f gene in Drosophila melanogaster encodes nuclear protein RNP-4F. This encoded protein is represented by homologs in other eukaryotic species, where it has been shown to function as an intron splicing assembly factor. Here, RNP-4F is believed to initially bind to a recognition sequence on U6-snRNA, serving as a chaperone to facilitate its association with U4-snRNA by intermolecular hydrogen bonding. RNA conformations are a key factor in spliceosome function, so that elucidation of changing secondary structures for interacting snRNAs is a subject of considerable interest and importance. Among the five snRNAs which participate in removal of spliceosomal introns, there is a growing consensus that U6-snRNA is the most structurally dynamic and may constitute the catalytic core. Previous studies by others have generated potential secondary structures for free U4- and U6-snRNAs, including the Y-shaped U4-/U6-snRNA model. These models were based on study of RNAs from relatively few species, and the popular Y-shaped model remains to be systematically re-examined with reference to the many new sequences generated by recent genomic sequencing projects. We have utilized a comparative phylogenetic approach on 60 diverse eukaryotic species, which resulted in a revised and improved U4-/U6-snRNA secondary structure. This general model is supported by observation of abundant compensatory base mutations in every stem, and incorporates more of the nucleotides into base-paired associations than in previous models, thus being more energetically stable. We have extensively sampled the eukaryotic phylogenetic tree to its deepest roots, but did not find genes potentially encoding either U4- or U6-snRNA in the Giardia and Trichomonas data-bases. Our results support the hypothesis that nuclear introns in these most deeply rooted eukaryotes may represent evolutionary intermediates, sharing characteristics of both group II and spliceosomal introns. An unexpected result of this study was discovery of a potential competitive binding site for Drosophila splicing assembly factor RNP-4F to a 5'-UTR regulatory region within its own premRNA, which may play a role in negative feedback control.

Project description:We have examined the distribution of RNA transcription and processing factors in the amphibian oocyte nucleus or germinal vesicle. RNA polymerase I (pol I), pol II, and pol III occur in the Cajal bodies (coiled bodies) along with various components required for transcription and processing of the three classes of nuclear transcripts: mRNA, rRNA, and pol III transcripts. Among these components are transcription factor IIF (TFIIF), TFIIS, splicing factors, the U7 small nuclear ribonucleoprotein particle, the stem-loop binding protein, SR proteins, cleavage and polyadenylation factors, small nucleolar RNAs, nucleolar proteins that are probably involved in pre-rRNA processing, and TFIIIA. Earlier studies and data presented here show that several of these components are first targeted to Cajal bodies when injected into the oocyte and only subsequently appear in the chromosomes or nucleoli, where transcription itself occurs. We suggest that pol I, pol II, and pol III transcription and processing components are preassembled in Cajal bodies before transport to the chromosomes and nucleoli. Most components of the pol II transcription and processing pathway that occur in Cajal bodies are also found in the many hundreds of B-snurposomes in the germinal vesicle. Electron microscopic images show that B-snurposomes consist primarily, if not exclusively, of 20- to 30-nm particles, which closely resemble the interchromatin granules described from sections of somatic nuclei. We suggest the name pol II transcriptosome for these particles to emphasize their content of factors involved in synthesis and processing of mRNA transcripts. We present a model in which pol I, pol II, and pol III transcriptosomes are assembled in the Cajal bodies before export to the nucleolus (pol I), to the B-snurposomes and eventually to the chromosomes (pol II), and directly to the chromosomes (pol III). The key feature of this model is the preassembly of the transcription and processing machinery into unitary particles. An analogy can be made between ribosomes and transcriptosomes, ribosomes being unitary particles involved in translation and transcriptosomes being unitary particles for transcription and processing of RNA.

Dataset Information

Targeting of U4/U6 small nuclear RNP assembly factor SART3/p110 to Cajal bodies.

Publications

Targeting of U4/U6 small nuclear RNP assembly factor SART3/p110 to Cajal bodies.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets