Annexin II is associated with mRNAs which may constitute a distinct subpopulation

Abstract

Protein-mRNA interactions affect mRNA transport, anchorage, stability and translatability in the cytoplasm. During the purification of three subpopulations of polysomes, it was observed that a 36-kDa protein, identified as annexin II, is associated with only one specific population of polysomes, namely cytoskeleton-associated polysomes. This association appears to be calcium-dependent since it was sensitive to EGTA and could be reconstituted in vitro. UV irradiation resulted in partial, EGTA-resistant cross-linking of annexin II to the polysomes. Binding of (32)P-labelled total RNA to proteins isolated from the cytoskeleton-bound polysomes on a NorthWestern blot resulted in a radioactive band having the same mobility as annexin II and, most importantly, purified native annexin II immobilized on nitrocellulose specifically binds mRNA. The mRNA population isolated from cytoskeleton-bound polysomes binds to annexin II with the highest affinity as compared with those isolated from free or membrane-bound polysomes. Interestingly, the annexin II complex, isolated from porcine small intestinal microvilli was a far better substrate for mRNA binding than the complex derived from transformed Krebs II ascites cells. When cytoskeleton-associated polysomes were split into 60 S and 40 S ribosomal subunits, and a peak containing mRNA complexes, annexin II fractionated with the mRNAs. Finally, using affinity purification of mRNA on poly(A)(+)-coupled magnetic beads, annexin II was only detected in association with messenger ribonucleoproteins (mRNPs) present in the cytoskeletal fraction (non-polysomal mRNPs). These results, derived from both in vitro experiments and cell fractionation, suggest that annexin II binds directly to the RNA moiety of mRNP complexes containing a specific population of mRNAs.

Epstein–Barr virus latent membrane protein 1 mediates serine 25 phosphorylation and nuclear entry of annexin A2 via PI‐PLC–PKCα/PKCβ pathway

“…Annexin A2 may participate in mRNA processing or transport. This conclusion has been supported by the evidence of its association with small ribonucleoprotein particles, its binding to cytoskeleton‐associated mRNA subpopulations, and the nuclear export signal in the annexin A2 N‐terminal residues 1–13 52, 53. Recent studies have shown that annexin A2 participates in c‐myc mRNA transport and increases the c‐myc expression level 54.…”

Domains I and IV of Annexin A2 Affect the Formation and Integrity of In Vitro Capillary-Like Networks

“…These functions are modulated via numerous post-translational modifications, including Tyr and Ser phosphorylation [1], [2], [3], indicating that the protein plays an important role in signal transduction. The ligands include Ca 2+ [1], [2], [3], anionic phospholipids [12], cholesterol [13], S100A10 (p11) [14], tissue plasminogen activator (tPA) and plasminogen/plasmin [15], F- and G-actin [16], [17], vascular endothelial (VE)-cadherin [18], specific mRNAs [19] and heparin [20]. The large number of ligands and posttranslational modifications of AnxA2 reflect its multicompartmental nature and multifunctionality.…”

Ubiquitinated annexin A2 is enriched in the cytoskeleton fraction

“…AnxA2 is enriched in the cytoskeleton fraction (Triton X‐100 insoluble fraction) derived from Krebs II cells from which it is released (Fig. 2 A and B, lane 2) by increasing the salt concentration to 130 mM KCl and the temperature to 20 °C [2,15]. In addition, 10 mM EGTA was added to promote the release of anxA2 associated with phospholipids in membranes and the cytoskeleton in a Ca 2+ ‐dependent manner.…”

“…Further purification was performed as described [13]. Subcellular fractionation of mouse Krebs II cells was performed essentially as described [2,15]. AnxA2 present in the cytoskeleton fraction [15] was released from the Triton X‐100 insoluble material by a buffer containing 10 mM triethanolamine (pH 7.4), 250 mM sucrose, 10 mM EGTA, 130 mM KCl, and 2 mM MgCl 2 .…”

“…Annexin A2 (anxA2) is a multifunctional Ca 2+ ‐, lipid‐, and actin‐binding protein implicated in a number of intracellular functions such as signal transduction, membrane trafficking and mRNA transport [1,2], as well as the regulation of membrane/cytoskeleton contacts and extracellular functions [1,3]. The anxA2 protomer is cleaved by chymotrypsin into a 33 kDa C‐terminal core domain, and a 3 kDa N‐terminal domain which consists of 30 amino acids of which the first 14 residues constitute the binding site for its S100 protein binding partner, p11 [4].…”