ABSTRACT
FR901464 is a potent antitumor natural product that binds to the splicing factor 3b complex and inhibits pre-mRNA splicing. Its analogue, meayamycin, is two orders of magnitude more potent as an antiproliferative agent against human breast cancer MCF-7 cells. Here, we report the picomolar antiproliferative activity of meayamycin against various cancer cell lines and multidrug-resistant cells. Time-dependence studies implied that meayamycin may form a covalent bond with its target protein(s). Meayamycin inhibited pre-mRNA splicing in HEK-293 cells but not alternative splicing in a neuronal system. Meayamycin exhibited specificity toward human lung cancer cells compared with nontumorigenic human lung fibroblasts and retained picomolar growth-inhibitory activity against multidrug-resistant cells. These data suggest that meayamycin is a useful chemical probe to study pre-mRNA splicing in live cells and is a promising lead as an anticancer agent.
Subject(s)
Antineoplastic Agents/pharmacology , Epoxy Compounds/pharmacology , Pyrans/pharmacology , RNA Precursors/metabolism , RNA Splicing/drug effects , RNA, Messenger/metabolism , Antineoplastic Agents/chemistry , Apoptosis , Cell Line, Tumor , Cell Proliferation , Cells, Cultured , Drug Resistance, Neoplasm , Epoxy Compounds/chemistry , Humans , Lung Neoplasms/drug therapy , Lung Neoplasms/metabolism , Pyrans/chemistry , Spiro Compounds/chemistry , Spiro Compounds/pharmacologyABSTRACT
Membrane-permeable compounds that reversibly inhibit a particular step in gene expression are highly useful tools for cell biological and biochemical/structural studies. In comparison with other gene expression steps where multiple small molecule effectors are available, very few compounds have been described that act as general inhibitors of pre-mRNA splicing. Here we report construction and validation of a set of mammalian cell lines suitable for the identification of small molecule inhibitors of pre-mRNA splicing. Using these cell lines, we identified the natural product isoginkgetin as a general inhibitor of both the major and minor spliceosomes. Isoginkgetin inhibits splicing both in vivo and in vitro at similar micromolar concentrations. It appears to do so by preventing stable recruitment of the U4/U5/U6 tri-small nuclear ribonucleoprotein, resulting in accumulation of the prespliceosomal A complex. Like two other recently reported general pre-mRNA splicing inhibitors, isoginkgetin has been previously described as an anti-tumor agent. Our results suggest that splicing inhibition is the mechanistic basis of the anti-tumor activity of isoginkgetin. Thus, pre-mRNA splicing inhibitors may represent a novel avenue for development of new anti-cancer agents.
Subject(s)
Antineoplastic Agents/pharmacology , Biflavonoids/pharmacology , RNA Precursors/metabolism , RNA Splicing/drug effects , Spliceosomes/metabolism , Cell Line , Dose-Response Relationship, Drug , Humans , RNA Precursors/genetics , RNA Splicing/physiology , Ribonucleoprotein, U4-U6 Small Nuclear/genetics , Ribonucleoprotein, U4-U6 Small Nuclear/metabolism , Ribonucleoprotein, U5 Small Nuclear/genetics , Ribonucleoprotein, U5 Small Nuclear/metabolism , Spliceosomes/geneticsABSTRACT
Over the past few years, issues related to the commitment and potential of reservoir precursor cells that reside in most tissues have been revisited. Many reports have documented either plasticity or de-differentiation of a number of precursor cells isolated from several tissues, including bone marrow, brain, and skeletal muscle. These findings have challenged the dogma that mononuclear cells derived from adult, post-mitotic tissues can differentiate and contribute only to the tissue from which they originate. Thus, much current research in stem cells is testing the therapeutic potential of these cells to deliver normal genes and their encoded proteins into damaged or injured tissues. This review will focus on muscle-derived precursor cells and their apparently heterogeneous nature and summarize some of the most recent findings and hypotheses on their characterization and practical use.