Developing rat brain as well as cultured astrocytes contain H1° mRNA-protein complexes

RNA-binding proteins (RBPs) regulate intracellular transport, pre-localization, 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 the results of a more detailed study on the expression and intracellular localization of some of these RBPs, such as hnRNP K and A1, and Hsc70, during rat brain development and in cultured rat astrocytes. We also investigated the presence in the complexes of PIPPin/CSD-C2 protein. 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. 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 hnRNP, previously found in the complexes, was found to be differentially expressed and localized during rat brain maturation. In particular, we found that nuclear levels of A1 increase in cultured astrocytes grown on a fibronectin-containing substrate, but decrease when cells are fed with Maat medium [7]. We finally report that sumoylated PIPPin, already found in neurons, is also present in the nuclei of cultured astrocytes. [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. [7] Cestelli et al., 1985, Brain Res 354:219-27.