MICROFILAMENT‐DEPENDENT MODULATION OF CYTOPLASMIC PROTEIN BINDING TO TNFα mRNA AU‐RICH INSTABILITY ELEMENT IN HUMAN LYMPHOID CELLS

Abstract

Cytoplasmic proteins with binding capability to AU-rich instability determinant sequences (ARE) of tumour necrosis factor alpha (TNFalpha) 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 TNFalpha 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.

Interleukin‐1‐inducible MCPIP protein has structural and functional properties of RNase and participates in degradation of IL‐1β mRNA

“…These data are in agreement with results obtained by Henics et al. [13], who showed that cytoskeleton proteins have binding capacity for proteins involved in mRNA metabolism. Moreover, cytoskeleton proteins, such as actin or tubulin, are thought to be crucial for compartmentalization and translation of various mRNAs, including those containing AU‐rich instability motifs in the 3′ UTR [14,15].…”

Actin Cytoskeleton Organization and Posttranscriptional Regulation of Endothelial Nitric Oxide Synthase During Cell Growth

“…34,35 Cytochalasin-induced disruption of lymphocyte microfilaments resulted in more stable IL-2 and tumor necrosis factor-␣ mRNAs, and this was associated with an altered subcellular localization of destabilizing RNA-binding proteins. These proteins could be immunoprecipitated with anti-actin antibodies.…”

Identification of a novel C1q family member in color crucian carp (Carassius auratus) ovary

“…A lot of studies have demonstrated that most of the genes with AU-rich element in the 3V-UTR of their mRNAs are the early response genes that regulate cell growth and body response to exogenous agents such as microbes, inflammatory and environmental stimuli. These genes mainly include three classes: cytokines, chemokines and oncogenes (Hel et al, 1998;Henics, 1999). Tumor necrosis factor (TNF), interferon and interferonstimulated genes belong to the kind of genes with AU-rich element (Stoecklin et al, 2003;Zhang et al, 2003;Zhang and Gui, 2004).…”