Distribution profile and in vivo RNA association of cytoplasmic AU-rich sequence binding proteins in various mammalian cells: effect of the organizational state of cellular architecture.

: With the aid of sequential detergent fractionation and label transfer techniques, in this study we monitored the distribution of cytoplasmic AU-rich sequence binding proteins (AUBP) in different cell types. We show here that cells of various origin display diverse AUBP profiles when the presence and abundance of AUBPs were compared in two major cytoplasmic compartments, the non-ionic detergent-soluble and -insoluble fractions. We also demonstrate that different RNA probes derived from AU-rich 3'-UTR elements of various cytokine and proto-oncogene mRNAs detect distinct AUBPs within the same cell. When the in vivo association of these proteins with AU-rich RNA was assessed using the combination of in vivo UV-crosslinking and label transfer methods, we found that detachment of monolayer cells by trypsinization or disruption of the microfilament network by Cytochalasin treatment prior to UV light exposure, led to selective changes in both the cytoplasmic distribution and in vivo RNA association of many AUBPs. These data indicate that the organizational state of cytoarchitecture may influence processes involved in AUBP-mediated mRNA metabolism.