Environmental toxins and toxicants are sources of oxidative stress in cells due to the production of reactive oxygen species (ROS), which can damage cellular components such as proteins and DNA. One of the most common products of DNA oxidation is 8-oxoguanine (OG) that becomes mispaired with adenine (A) during DNA replication, ultimately producing G:C to T:A transversion mutations. MUTYH is a base excision repair (BER) glycosylase that initiates the repair of OG:A mispair by removing the adenine base. Notably, inherited germline mutations in the <i>MUTYH </i>gene can alter enzyme function and lead to a condition called MUTYH-associated Polyposis (MAP), which increases lifetime risk of colorectal cancer. However, proper functioning of MUTYH under high ROS conditions could lead to genomic instability due to higher levels of MUTYH generated AP sites that may lead to single and double stranded breaks in DNA. Due to this conundrum, we wish to explore the regulatory role of ROS on the activity of MUTYH. We hypothesize that high ROS conditions regulate MUTYH activity through the oxidation of exposed Cys residues. We have also previously identified a Cys-coordinate Zn(II) site which is required for MUTYH repair activity, and we propose that oxidation of one of these Cys residues may lead to loss of Zn(II) and reduced activity. In this work, we characterize the <i>in vitro</i> effects of different oxidants on MUTYH activity and conduct cellular assays to identify the ROS reactive moieties in MUTYH and understand how ROS exposure affects enzymatic activity and cell survival.

Investigating the role of cysteine oxidation by environmentally induced oxidative stress on the DNA glycosylase MUTYH

2019 Fall National Meeting

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