Environmental genotoxic carcinogens target numerous proto-oncogenes (and tumor-suppressor genes) to
induce point mutations in key codons, leading to oncogene activation. Oncogene activation disturbs a wide range
of cellular processes, including alterations in the genomic and molecular landscape of precancerous cells that
contributes to genomic instability, which accelerates chromosomal breakages, rearrangements and promotes
tumorigenesis. Part of this cellular turmoil involves early deregulation of physiologic DNA replication, known as
replication stress. Oncogene-induced replication stress is an early driver of genomic instability and is attributed
to a plethora of factors, most notably aberrant origin firing, replication-transcription collisions, and defective
nucleotide metabolism. Despite much progress in the field, the mechanisms through which oncogenes induce
replication stress, particularly in early events leading to carcinogenesis, remains poorly understood. Major gaps
in our knowledge of this process include: 1) What are the early steps that contributes to oncogene-induced
replication stress in precancerous cells? and 2) How are replication stress response factors coordinated to
overcome/resolve replication stress in a time-dependent manner? Research into these questions have been
hampered by limitations inherent in using traditional cancer cell lines and cell biological approaches that may or
may not accurately reflect the temporal and spatial regulation of the DNA replication stress response in a more
physiologically-relevant in vitro pre-cancer model.
In this application, we propose to address these knowledge gaps by using cancer-relevant primary human
cells to explore how oncogene-induced replication stress can shape genome-wide replication fork initiation and
termination sites, focusing on how these changes in the replication program will impact genome integrity.
Furthermore, we will determine how recently discovered players in the replication stress response pathway are
regulated to subvert oncogene-induced replication stress. Deciphering the mechanisms that contribute to this
early replication stress response at the genome-wide level may provide new avenues for targeted cancer
treatment. The questions we address here will set the stage for future investigations that include (but are not
limited to) analyses of how environmental genotoxins may influence oncogene-induced replication stress to
exacerbate genomic instability to accelerate tumorigenesis.