Molecular, Cell, Development (MCD) Seminar Series - McMaster University
2008-09 || 2009-10 || 2010-11 || 2011-12 || 2012-13

Molecular, Cell, Development (MCD) SEMINAR SERIES
Department of Biology

Speaker: Dr. Jean-Yves Masson

Date: Friday 23rd, November, 2012
Time: 12 noon
Location: HSC 1A5

Title: Functions of Fanconi anemia proteins in DNA double-strand break repair

It has been increasingly clear that tumour formation can be triggered by mutations in enzymes involved in the surveillance of genome integrity. PALB2 is a recently identified BRCA2 interacting protein, essential for BRCA2 anchorage to nuclear structures and for its function in double-strand break repair. Inherited mutations in PALB2 are associated with a predisposition for ovarian, breast and pancreatic cancers and Fanconi Anemia. Fanconi anemia patients have congenital defects, commonly short stature, abnormalities of the skin, arms, head, eyes, kidneys, and ears, and cancer. The basis of the tumorigenic potential of PALB2 is thought to be related to functions in homologous recombination, however, due to the complexity of this mechanism, the biochemical contribution of PALB2 in homologous recombination is still poorly understood.

Therefore, we developed a new procedure to obtain PALB2 in a highly purified form in baculovirus-infected cells. We have shown that PALB2 directly interacts with the RAD51 recombinase and strongly stimulates strand invasion, a vital step of homologous recombination. We present also a thorough analysis of PALB2 structure-function. In vitro studies helped us to establish that PALB2 has two DNA binding domains, two RAD51-interacting domains, and a dimerization domain. We report that the N-terminal coiled-coil motif of PALB2 regulates it self-association and homologous recombination.

One view of homologous recombination is to find a template for DNA synthesis from the resected 3’-OH molecule. This occurs during DSB repair, in broken or stalled replication forks. We found that PALB2 stimulates polymerase eta to initiate DNA synthesis by homologous recombination. PALB2 and BRCA2 and pol eta co-localize at collapsed replication forks after hydroxyurea treatment. Moreover, PALB2 interacts with pol eta in vitro and in vivo. Knockdown of PALB2 is required to sustain the recruitment of pol eta at collapsed replication forks. We conclude that PALB2 has crucial roles in the initiation of recombination-associated DNA synthesis by DNA polymerase eta leading to DNA repair.