Article

The La RNA-binding protein interacts with the vault RNA and is a vault-associated protein.

Department of Biological Chemistry, The David Geffen School of Medicine, University of California-Los Angeles, 33-131 CHS Mail Code 173717, 10833 Le Conte Avenue, Los Angeles, CA 90095-1737, USA.
Journal of Biological Chemistry (Impact Factor: 4.6). 11/2002; 277(43):41282-6. DOI: 10.1074/jbc.M206980200
Source: PubMed

ABSTRACT Vaults are highly conserved ubiquitous ribonucleoprotein particles with an undefined function. Three protein species (p240/TEP1, p193/VPARP, and p100/MVP) and a small RNA comprise the 13-MDa vault particle. The expression of the unique 100-kDa major vault protein is sufficient to form the basic vault structure. Previously, we have shown that stable association of the vault RNA with the vault particle is dependent on its interaction with the p240/TEP1 protein. To identify other proteins that interact with the vault RNA, we used a UV-cross-linking assay. We find that a portion of the vault RNA is complexed with the La autoantigen in a separate smaller ribonucleoprotein particle. La interacts with the vault RNA (both in vivo and in vitro) presumably through binding to 3'-uridylates. Moreover, we also demonstrate that the La autoantigen is the 50-kDa protein that we have previously reported as a protein that co-purifies with vaults.

0 Bookmarks
 · 
58 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: Endogenous vaults are ribonucleoproteins expressed throughout various cell types and across numerous species. Several central nervous system (CNS) tumors have been reported to exhibit high levels of major vault protein (MVP). The vault has been hypothesized to play a role in cellular transport. Although further studies are needed to elucidate the mechanisms of endogenous vault function, these advances may enable the development of targeted therapies to prevent cancer cells from acquiring MVP-related drug resistance. In addition, they seem suited for use as nanocapsules for delivering various therapeutic agents and immunogenic proteins, representing a promising prospect for CNS tumor immunotherapy.
    Neurosurgery clinics of North America 07/2012; 23(3):451-8. · 1.73 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Telomeres, the ends of linear chromosomes, safeguard against genome instability. The enzyme responsible for extension of the telomere 3' terminus is the ribonucleoprotein telomerase. Whereas telomerase activity can be reconstituted in vitro with only the telomerase RNA (hTR) and telomerase reverse transcriptase (TERT), additional components are required in vivo for enzyme assembly, stability and telomere extension activity. One such associated protein, dyskerin, promotes hTR stability in vivo and is the only component to co-purify with active, endogenous human telomerase. We used oligonucleotide-based affinity purification of hTR followed by native gel electrophoresis and in-gel telomerase activity detection to query the composition of telomerase at different purification stringencies. At low salt concentrations (0.1 M NaCl), affinity-purified telomerase was 'supershifted' with an anti-dyskerin antibody, however the association with dyskerin was lost after purification at 0.6 M NaCl, despite the retention of telomerase activity and a comparable yield of hTR. The interaction of purified hTR and dyskerin in vitro displayed a similar salt-sensitive interaction. These results demonstrate that endogenous human telomerase, once assembled and active, does not require dyskerin for catalytic activity. Native gel electrophoresis may prove useful in the characterization of telomerase complexes under various physiological conditions.
    Nucleic Acids Research 12/2011; 40(5):e36. · 8.81 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Major vault protein (MVP) is the predominant constituent of the vault particle, the largest known ribonuclear protein complex. Although emerging evidences have been establishing the links between MVP (vault) and multidrug resistance (MDR), little is known regarding exactly how the MDR activity of MVP is modulated during cellular response to drug-induced DNA damage (DDR). Bleomycin (BLM), an anti-cancer drug, induces DNA double-stranded breaks (DSBs) and consequently triggers the cellular DDR. Due to its physiological implications in hepatocellular carcinoma (HCC) and cell fate decision, 14-3-3ε was chosen as the pathway-specific bait protein to identify the critical target(s) responsible for HCC MDR. By using LC-MS/MS-based proteomic approach, MVP was first identified in the BLM-induced 14-3-3ε interactome formed in HCC cells. Biological characterization revealed that MVP possesses specific activity to promote the resistance to the BLM-induced DDR. On the other hand, 14-3-3ε enhances BLM-induced DDR by interacting with MVP. Mechanistic investigation further revealed that 14-3-3ε, in a phosphorylation-dependent manner, binds to the phosphorylated sites at both Thr52 and Ser864 of the monomer of MVP. Consequently, the phosphorylation-dependent binding between 14-3-3ε and MVP inhibits the drug-resistant activity of MVP for an enhanced DDR to BLM treatment. Our findings provide an insight into the mechanism underlying how the BLM-induced interaction between 14-3-3ε and MVP modulates MDR, implicating novel strategy to overcome the chemotherapeutic resistance through interfering specific protein-protein interactions.
    Journal of Proteome Research 04/2013; · 5.06 Impact Factor

Leonard H Rome