Function of ZFAND3 in the DNA Damage Response

The DNA-damage response (DDR) functions to maintain genomic integrity and prevent tumorigenesis. Cells in human precancerous lesions contain high levels of DNA damage, potentially resulting from unresolved problems accrued during DNA replication. Such replication stress can arise from stalling of replication forks at DNA lesions. The dynamic coordination of mechanisms that detect and repair these damaged replication forks is the subject of this research. Several mechanisms to repair a damaged fork and restart replication depend on tumor-suppressor proteins such as BRCA1 (breast cancer 1) and checkpoint kinase signaling via ATR and ATM. A significant unanswered question is how these DDR proteins are spatially and temporally regulated during replication stress. We have developed a new method termed iPOND (isolation of proteins on nascent DNA) to examine DDR protein dynamics and functions at moving and stalled replication forks in mammalian cells. We used iPOND to define the dynamics of chromatin assembly and maturation. Furthermore, we show that stalled and collapsed replication forks contain different DDR protein complexes. Persistent replication fork stalling leads to fork collapse and recruitment of DSB repair proteins such as Rad51. Our systematic study of these mechanisms reveals new insights into how damaged forks are repaired and why defects in specific DDR pathways in cancer can cause genome instability during DNA replication. These studies have implications for understanding breast cancer etiology. The original document contains color images.