De Majo, Daniela (2010) Functional characterization of NCOA4 protein in Xenopus laevis egg extracts. [Tesi di dottorato] (Inedito)

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Tipologia del documento:	Tesi di dottorato
Lingua:	English
Titolo:	Functional characterization of NCOA4 protein in Xenopus laevis egg extracts
Autori:	Autore Email De Majo, Daniela danielademajo@hotmail.it
Data:	30 Novembre 2010
Numero di pagine:	81
Istituzione:	Università degli Studi di Napoli Federico II
Dipartimento:	Biologia e patologia cellullare e molecolare "L. Califano"
Scuola di dottorato:	Medicina molecolare
Dottorato:	Oncologia ed endocrinologia molecolare
Ciclo di dottorato:	23
Coordinatore del Corso di dottorato:	nome email Santoro, Massimo [non definito]
Tutor:	nome email Carlomagno, Francesca persfra@tin.it
Data:	30 Novembre 2010
Numero di pagine:	81
Parole chiave:	thyroid cancer; DNA replication; MCM proteins; helicase; nuclear receptor coactivator;
Settori scientifico-disciplinari del MIUR:	Area 06 - Scienze mediche > MED/04 - Patologia generale
Depositato il:	13 Dic 2010 15:03
Ultima modifica:	30 Apr 2014 19:45
URI:	http://www.fedoa.unina.it/id/eprint/8253

Abstract

This dissertation is focused on the functional characterization of NCOA4 protein in Xenopus laevis egg extracts. In human papillary thyroid carcinoma the rearrangement of RET tyrosine kinase (TK) domain with the 5’ portion of a number of heterologous genes, generates the RET/papillary thyroid carcinoma (PTC) oncogenes. One of the most frequent variant of RET/PTC rearrangements is the RET/PTC3 oncogene, generated by the fusion of the RET gene TK domain encoding sequence with the first exons and the promoter region of a gene named NCOA4 (ELE1/ARA70/RFG). By yeast two-hybrid system, we previously isolated the Mini-Chromosome Maintenance 7 (MCM7) protein as an NCOA4 protein interactor. MCM7 is a member of the heteroexameric MCM 2-7 complex, a key component of the pre- Replication Complex (pre-RC), and the major helicase of the DNA replication forks. Exogenously added recombinant protein NUS-NCOA4 in activated Xenopus laevis egg extracts is able to inhibit DNA replication by interacting with MCM7 protein and blocking MCM2-7 complex helicase activity. Here we show the cloning and the functional characterization of Xenopus laevis orthologous of NCOA4 gene, XNCOA4α and β. XNCOA4 and MCM7 proteins interact at the endogenous level in Xenopus laevis egg extracts. In XNCOA4 depleted extracts, DNA replication rate was approximately doubled with an increase of the single strands binding protein RPA and PCNA loading, suggesting an improvement of helicase activity, while Pre-RC (such as Cdc6 and MCM7) or Pre-IC (such as Cdc45 and GINS) components were not affected in their binding to DNA. Finally, we analyzed NCOA4 expression in thyroid cell line and human thyroid carcinomas, observing a reduction of NCOA4 level in few PTC samples and all ATC samples analyzed. Our results suggest that NCOA4 is a novel regulator of DNA replication and NCOA4/RET rearrangement might represent a novel paradigm of a cancer-associated chromosome rearrangement that directly targets a gene that controls DNA replication.

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