A DNA double strand break (DSB) which constitutes severing of a chromosome into two parts is one of the most lethal types of DNA damage because it can lead to loss of genetic information, or other forms of chromosomal rearrangements. DSBs can occur spontaneously mainly during DNA replication or be caused by external DNA damaging agents. One mechanism of DSB repair is via error-free homologous recombination (HR), a process in which missing genetic information resulting from the break is copied from another similar undamaged chromosomal region. Although HR has been studied extensively, a complete understanding of the mechanisms that govern this process has remained elusive. In recent years, multiple recombination pathways have been identified that may produce gene conversions, deletions, translocations or duplications. Analyzing the genetic requirements for all these recombination outcomes could be a daunting task. Most of the many pathways of repair have been studied independently and to our knowledge a way of simultaneously studding the contributions of all the repair pathways has not been possible. Here we propose the development of a novel assay that can simultaneously study the contribution of most recombination pathways through a simple genetic screen. We then intend to use this assay to assess the function of two chromatin remodeling genes in homologous recombination. We believe that this assay will be of tremendous interest in the field of double strand break repair and will greatly enhance our understanding of DNA damage repair. !
Inaccurate repair of DNA damage is a primary determinant of cellular transformation and carcinogenesis. In recent years, it has been recognized that in addition to progressive accumulation of mutations, cancer cells are also characterized by a high level of chromosomal instability (CIN) which comes in two forms, numerical instability (nCIN) and structural instability (sCIN). Numerical instability constitutes losing or gaining an extra chromosome because of failure of the chromosome separation apparatus (spindle) during cell division. Structural instability refers to different forms of chromosomal aberrations such as deletions, duplications, inversions and translocations. These sCINs arise as a result of improperly repaired DNA double strand break and this grant focuses on developing an assay to better understand double strand break repair. Understanding the mechanisms that govern DNA double strand break repair is paramount to the development of molecular mechanisms that drive tumor formation.