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Alessandra Montecucco


IGM-CNR, Via Abbiategrasso, 207 - 27100 Pavia, Italy

tel: +39-0382-546351
fax: +39-0382-422286
E-mail: montecucco@igm.cnr.it

 

 

Curriculum

  • Senior Researcher, Institute of Molecular Genetics of CNR, Pavia
  • Visiting Scientist, Imperial Cancer Research Fund, London (UK)
  • EMBO Fellow, Institut de Recherches Scientifiques sur le Cancer, IRSC-CNRS, Villejuif, France 
  • Member of the Italian Society of Biophysics and Molecular Biology (http://www.sibbm.org/), Associazione di Biologia Cellulare e del Differenziamento (http://abcd-it.org), and American Society for Biochemistry and Molecular Biology (http://www.asbmb.org/) 

 

Scientific Interests

BIOCHEMICAL AND FUNCTIONAL CHARACTERIZATION OF ATP-DEPENDENT DNA LIGASES

DNA ligases catalyze the joining of single-strand or double-strand breaks between adjacent 3’-hydroxyl and 5’-phosphate termini in the phosphodiester backbone of double-strand DNA. For this reason they play a vital role in DNA metabolism. Most eukaryotic DNA ligases use ATP as a cofactor. In mammalian cells there are three DNA ligases called DNA ligase I, III and IV. DNA strand breaks can occur as a result either of the direct action of DNA damaging agents or as reaction intermediates during DNA replication, repair and recombination; therefore the sealing of these breaks by DNA ligase is critical for maintaining genome integrity. Most of the work carried out in my laboratory has led to the characterization of human DNA ligase I that is required for chromosomal DNA replication as well as for DNA-repair pathways.

 

CELLULAR RESPONSE TO DNA DAMAGE IN HUMAN CELLS

We are currently studying the cell response to chronic replication-dependent DNA damage using as a model system 46BR.1G1 cells established from a patient with a genetic syndrome due to DNA ligase I haplo-insufficiency. We have extensively characterized these cells and found that they show a delayed maturation of Okazaki fragments, which results in the accumulation of single- and double-stranded DNA breaks. Notably, the replication-dependent DNA damage in LigI-deficient cells fails to halt cell cycle progression and to induce apoptosis. Actually, 46BR.1G1 cells display only a moderate delay in cell cycle progression and do not activate the S-phase specific ATR/Chk1 checkpoint pathway while the ATM/Chk2 pathway is constitutively activated at basal level. The strategy used by LigI-deficient cells to cope with this higher basal level of DNA damage is presently unknown. Recent results in our laboratory indicate that a number of pre-mRNA processing factors are regulated during the DNA damage response, shifting the alternative splicing pattern of target genes to control cell survival. This finding highlights the existence of a complex regulatory network that links alternative splicing decisions to DNA replication stress and DNA damage.

 

DNA REPLICATION

In mammalian cells DNA replication takes place at discrete nuclear sites called replication foci where newly synthesized DNA accumulates. Colocalization on replication foci of replicative enzymes gave rise to the idea that replication takes place within factories. The number and size of the replication factories vary throughout S phase according to a program that reflects the replication of various portions of the genome. Our group contributed to the analysis of several aspects. We have identified a short motif, that we called replication factory targeting sequence (RFTS), as the determinant sufficient to target a protein to replication factories. The identification of the RFTS opens the possibility to disassemble the factories by targeting specific peptides. This perspective could be relevant in the search of new anti-proliferative drugs. The RFTS overlaps an evolutionary conserved binding site for PCNA. We have also shown that cell cycle dependent phosphorylation of replicative factors is involved in the dynamic program of replication factories. Finally we have shown that the ordered assembly and disassembly of replication factories is monitored by the cell cycle checkpoints and that the type of DNA damage, its distribution relative to the moving fork and the mechanism involved in the DNA damage recognition could determine the choice between stabilization and dispersal of replication factories in S phase. 

 

 

 

List of Publications


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