Expression and intracellular localization of H1° mRNA-containing complexes in developing rat brain and astrocytes

Abstract

INTRODUCTION: Post-transcriptional regulation of gene expression relies on RNA-binding proteins (RBPs), which regulate intracellular transport, stability, and translation of mRNAs [1]. We previously identified a set of proteins which interact with mRNAs encoding H1° and H3.3 histones [2-5]. All these proteins are probably part of a ribonucleoprotein particle [6]. Here we report more details on the expression and intracellular localization of some of these RBPs, during rat brain development and in isolated rat astrocytes. METHODS: Affinity chromatography was performed as already described [6]. Preparation of total lysates and cellular sub-fractions was done as reported in [3]. Possible co-localization of Hsc70 with CSD-C2 in cultured astrocytes was analysed by immunofluorescence microscopy. RESULTS: The presence of Hsc70 chaperone in the already identified ribonucleoprotein complex [6] was confirmed by affinity chromatography. We also found that the complex itself is present not only in the nuclear extracts, but also in the cytoplasmic fraction. Moreover, A1 and K hnRNPs, previously found in the complexes, were found to be differentially expressed and localized during rat brain maturation; an increase in A1 expression was also demonstrated in cultured astrocytes grown on a fibronectin-containing substrate. We finally report that sumoylated PIPPin, already found in neurons, is also present in the nuclei of cultured astrocytes. CONCLUSIONS: We confirmed the existence of a group of proteins able to interact with H1°/H3.3 mRNAs. These proteins are, however, differentially expressed during brain maturation and also show different subcellular localization. [1] Di Liegro et al. 2014, Int J Mol Med 33:747-62. ; [2] Scaturro et al. 1998, J Biol Chem 273:22788-91.; [3] Nastasi et al. 1999, J Biol Chem 274:24087-93. [4] Sala et al. 2007, Int J Mol Med 19:501-9. [5] Saladino et al. 2012, Int J Mol Med 29:141-5 [6] Di Liegro et al. 2013, Neuroscience 229:71-6.