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MICROFILAMENT‐DEPENDENT MODULATION OF CYTOPLASMIC PROTEIN BINDING TO TNFα mRNA AU‐RICH INSTABILITY ELEMENT IN HUMAN LYMPHOID CELLS
Author(s) -
Henics Tamás
Publication year - 1999
Publication title -
cell biology international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.932
H-Index - 77
eISSN - 1095-8355
pISSN - 1065-6995
DOI - 10.1006/cbir.1999.0418
Subject(s) - jurkat cells , biology , microfilament , cytoplasm , microbiology and biotechnology , messenger rna , rna binding protein , cytoskeleton , actin , cell , t cell , biochemistry , immunology , immune system , gene
Cytoplasmic proteins with binding capability to AU‐rich instability determinant sequences (ARE) of tumour necrosis factor α (TNFα) mRNA 3′ untranslated region (3′UTR) were assessed in human lymphoid cells. In vitro label transfer experiments using wild type as well as mutant sequences in which the 70 nucleotide‐long AUUUA pentamer‐containing portion of the 3′UTR had been deleted conferred binding specificity to five major activities of 22/25‐, 38/40‐, 50‐, 60‐ and 80‐kDa proteins in cytoplasmic extracts of peripheral blood mononuclear cells (PBMCs). Cytochalasin‐induced disarrangement of the F‐actin‐based microfilament system led to a Triton X‐100‐insoluble to soluble redistribution of these binding activities. No such changes were observed in Jurkat tumour cells. Combination of in vivo UV‐crosslinking and in vitro label transfer experiments revealed considerable differences in RNA association between proteins of the same cell type as well as between proteins of identical molecular weight (Mw) derived from either PBMCs or Jurkat cells. Our findings may explain some aspects of differential regulation of interleukin 2 (IL‐2) and TNFα mRNA stability upon microfilament disruption in human PBMCs observed in an earlier study. These results also suggest that the physical state of cytoplasmic structural environment might contribute to important regulatory processes regarding key elements of eukaryotic mRNA metabolism, such as modulation of stability. Finally, these data highlight the possibility that the often observed disorganization of the cytoskeleton in tumour cells may partly be responsible for the maintenance of the neoplastic state, a phenomenon that potentially involves ARE‐AUBP interactions.