Zorro locked nucleic acid induces sequence-specific gene silencing.

Locked nucleic acids (LNAs) are synthetic analogs of nucleic acids that contain a bridging methylene carbon between the 2' and 4' positions of the ribose ring. In this study, we generated a novel sequence-specific antigene molecule "Zorro LNA", which simultaneously binds to both strands, and that induced effective and specific strand invasion into DNA duplexes and potent inhibition of gene transcription, also in a cellular context. By comparing the Zorro LNA with linear LNA as well as an optimized bisPNA (peptide nucleic acid) oligonucleotide directed against the same target sites, respectively, we found that the Zorro LNA construct was unique in its ability to arrest gene transcription in mammalian cells. To our knowledge, this is the first time that in mammalian cells, gene transcription was blocked by a nucleic acid analog in a sequence-specific way using low but saturated binding of a blocking agent. This offers a novel type of antigene drug that is easy to synthesize.

Inducible H1 promoter-driven lentiviral siRNA expression by Stuffer reporter deletion.

Introduction of 19-23-bp small interfering RNA (siRNA) into mammalian cells has become a standard procedure to downregulate mRNA with high efficacy. siRNAs can be introduced into cells either as synthetic duplexes or as hairpin structures produced by Pol III promoter-driven vectors. Pol III promoter-expressed small hairpin RNAs (shRNAs) offer a great possibility for the production of endogenous siRNA, which can be used for stable siRNA production in vivo. A major drawback of this strategy is the incapability of detecting rapidly occurring cellular responses. Here, we present a lentiviral shRNA-producing vector system, which can be induced by CRE recombinase enzyme to overcome these limitations. Following the addition of CRE, the pLIND (LentiINDucible) will activate siRNA production by deleting EGFP and a stop cassette between the promoter and siRNA oligo. Target gene downregulation capacity was comparable to that of a noninducible siRNA system.

Bruton's tyrosine kinase: cell biology, sequence conservation, mutation spectrum, siRNA modifications, and expression profiling.

Bruton's tyrosine kinase (Btk) is encoded by the gene that when mutated causes the primary immunodeficiency disease X-linked agammaglobulinemia (XLA) in humans and X-linked immunodeficiency (Xid) in mice. Btk is a member of the Tec family of protein tyrosine kinases (PTKs) and plays a vital, but diverse, modulatory role in many cellular processes. Mutations affecting Btk block B-lymphocyte development. Btk is conserved among species, and in this review, we present the sequence of the full-length rat Btk and find it to be analogous to the mouse Btk sequence. We have also analyzed the wealth of information compiled in the mutation database for XLA (BTKbase), representing 554 unique molecular events in 823 families and demonstrate that only selected amino acids are sensitive to replacement (P < 0.001). Although genotype-phenotype correlations have not been established in XLA, based on these findings, we hypothesize that this relationship indeed exists. Using short interfering-RNA technology, we have previously generated active constructs downregulating Btk expression. However, application of recently established guidelines to enhance or decrease the activity was not successful, demonstrating the importance of the primary sequence. We also review the outcome of expression profiling, comparing B lymphocytes from XLA-, Xid-, and Btk-knockout (KO) donors to healthy controls. Finally, in spite of a few genes differing in expression between Xid- and Btk-KO mice, in vivo competition between cells expressing either mutation shows that there is no selective survival advantage of cells carrying one genetic defect over the other. We conclusively demonstrate that for the R28C-missense mutant (Xid), there is no biologically relevant residual activity or any dominant negative effect versus other proteins.

Silencing of Bruton's tyrosine kinase (Btk) using short interfering RNA duplexes (siRNA).

Tec family tyrosine kinases, Bruton's tyrosine kinase (Btk), Itk, Bmx, Tec, and Txk, are multi-domain proteins involved in hematopoietic signaling. Here, we demonstrate that human Btk protein can transiently be depleted using double-stranded short RNA interference (siRNA) oligonucleotides. Imaging and Western blotting analysis demonstrate that Btk expression is down regulated in heterologous systems as well as in hematopoietic lineages, following transfection or microinjection of Btk siRNA duplexes. The induction of histamine release, a pro-inflammatory mediator, in RBL-2H3 mast cells was reduced by 20-25% upon Btk down regulation. Similar, results were obtained when the Btk activity was inhibited using the kinase blocker LFM-A13. These results demonstrate a direct role of Btk for the efficient secretion of histamine in allergic responses.

Functional interaction of caveolin-1 with Bruton's tyrosine kinase and Bmx.

Bruton's tyrosine kinase (Btk), a member of the Tec family of protein-tyrosine kinases, has been shown to be crucial for B cell development, differentiation, and signaling. Mutations in the Btk gene lead to X-linked agammaglobulinemia in humans and X-linked immunodeficiency in mice. Using a co-transfection approach, we present evidence here that Btk interacts physically with caveolin-1, a 22-kDa integral membrane protein, which is the principal structural and regulatory component of caveolae membranes. In addition, we found that native Bmx, another member of the Tec family kinases, is associated with endogenous caveolin-1 in primary human umbilical vein endothelial cells. Second, in transient transfection assays, expression of caveolin-1 leads to a substantial reduction in the in vivo tyrosine phosphorylation of both Btk and its constitutively active form, E41K. Furthermore, a caveolin-1 scaffolding peptide (amino acids 82--101) functionally suppressed the autokinase activity of purified recombinant Btk protein. Third, we demonstrate that mouse splenic B-lymphocytes express substantial amounts of caveolin-1. Interestingly, caveolin-1 was found to be constitutively phosphorylated on tyrosine 14 in these cells. The expression of caveolin-1 in B-lymphocytes and its interaction with Btk may have implications not only for B cell activation and signaling, but also for antigen presentation.