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Title: Characterization of the interaction between nucleophosmin (NPM) and highmobility group a (HMGA) proteins.
Authors: Jakimovska, Frosina
Supervisore/Tutore: Manfioletti, Guidalberto
Issue Date: 1-Apr-2008
Publisher: Università degli studi di Trieste

HMGA proteins are members of the high mobility group (HMG) non-histone, architectural chromosomal proteins. The HMGA family consists of: A1a, A1b and A2, the first two being isoforms produced by alternative splicing. These are small proteins, about 100aa residues long, characterized by three basic stretches of AT-hooks which bind to the AT-rich sequences on the DNA minor groove. They are normally present in rapidly proliferating cells (embryo) whereas upon differentiation the levels of these proteins decrease until they are nearly absent from adult cells. Overexpression of these proteins has been correlated with various types of neoplastic transformations.
The interaction network of HMGA has been an object of study for years in our laboratory and one of the most intriguing protein-protein interactions studied is the one between HMGA and nucleophosmin.
Nucleophosmin (NPM, B23, numatrin or NO38) is one of the most abundant phosphoproteins, mainly localized in the nucleoli but it also shuttles between the nucleus and the cytoplasm. This versatile protein has been proven to be involved in various cellular functions and related to both proliferative and growth-suppressive roles in the cell.
The first evidence of the interaction HMGA2-NPM in our lab has been obtained by in vitro assays (affinity chromatography).
The step ahead was to see if this interaction occurs in vivo and if it does, to try to find ts functional significance. Thus,immunoprecipitation (IP) experiments were performed.The first one gave the proof thet interaction between HMGA2 protein and NPM (transfected and endogenous) occurs. The second IP gave the evidence that interaction occurs between HMGA1a and NPM too.
This in vivo protein-protein interaction was to be given a functional significance. We tested by siRNA HMGA1a treatment if downregulation of HMGA1a expression influences the expression of the SOD2 gene (regulated by NPM). The effect of the HMGA1a silencing has proven to be very slight on the SOD2 gene (a 14% of expression reduction).
EMSA experiments have been performed in order to test the effect of NPM on the DNA binding properties of the HMGA2 protein with the DNA probes E3 and HCRII. In both cases it has been observed that NPM increases the DNA binding affinity of the HMGA2 protein.
Keywords: HMGA proteins, Nucleophosmin
Type: Doctoral Thesis
Language: en
Settore scientifico-disciplinare: BIO/11 BIOLOGIA MOLECOLARE
NBN: urn:nbn:it:units-7221
Appears in Collections:Scienze biologiche

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