Prof. Dr. Lopes Massimo

Main Field(s) of Research, Abstract
DNA replication represents a crucial, but potentially dangerous process that cells have to complete in order to undergo cellular division. A failure to properly maintain the integrity of replicating chromosomes inevitably leads to genome instability, which is an early event in tumorigenesis. Remarkably, most of the common anti-cancer drugs also interfere with the mechanism of DNA replication, relying on the generic observation that cancer cells, intrinsically deficient for DNA repair and cell cycle checkpoints, are sensitized to DNA damaging agents. Despite the importance of replication stress in both cancer onset and therapy, little structural and genetic information is available on its underlying mechanisms in normal and cancer cells.
During the first years of my scientific career, I combined genetics and structural techniques (bi-dimensional DNA gel electrophoresis, electron microscopy) to investigate yeast DNA replication challenged by different types of stress (nucleotide depletion, DNA damage) and to elucidate the role of checkpoint and DNA repair factors in these processes. Recently, I have implemented these and other techniques in the mammalian cell culture system and I now plan to approach new biological questions working in parallel in yeast and higher eukaryotic systems.
The first aim of our research will be to gain structural information about the pathological transitions leading to genome instability during unperturbed DNA replication. By direct structural analysis of relevant cell culture and animal models of tumorigenesis, we aim to identify specific defects in DNA synthesis and chromatin modulation at replication forks that might account for the checkpoint activation observed in early precancerous lesions. At a later stage, we plan to extend these analyses to clinical samples.
Besides “whole genome” analysis, we also plan to focus our studies on microsatellites (trinucleotide repeats, TNR), as a paradigm for unstable chromosomal domains. Taking advantage of TNR-containing plasmids, we will test the role of candidate mammalian factors in the stability of these tracts during replication. By a combination of molecular and structural biological approaches, we aim to isolate defined abnormal DNA structures, suspected to associate with the onset of instability during TNR replication, and use them to generate a simple read-out of genomic instability arising at replicating chromosomes, in an attempt to identify novel mammalian factors actively preventing genome instability during DNA replication.
A third aim of our research will be to visualize by structural approaches the molecular transactions taking place on replicating chromosomes in response to established and novel anti-cancer drugs. By performing this analysis in both yeast and mammalian cells, and by comparing wild type cells with cell lines specifically defective in cancer-associated factors, we aim to gain new insights into the mechanism of action of these compounds and to characterize the cellular factors that play key roles in their cytotoxicity.

Main Fields of Research, Keywords
DNA replication, genome instability, early tumorigenesis, repetitive DNA sequences, cancer chemotherapeutics, genetics and structural approaches.

Special Techniques and Equipment
Standard methods of cellular and molecular biology; structural investigation techniques for DNA replication (DNA 2D gels, electron microscopy, molecular DNA combing, etc.).

Education and Training
The institute hosts regular seminars with distinguished speakers from Switzerland and abroad. We also hold regular journal clubs, data clubs and group meetings.