to DNA. Next, Rad-9 is recruited to the site, this time without Rad-1 and Hus-1, and is phosphorylated by ATR again. This activation induces the formation of Rad-9 oligomers around the damaged chromosomes, which serve as a recruiter for CHK-2. Upon arrival at the damage site, CHK-2 is phosphorylated by ATR and released from the damage site to bind to its targets that inhibit the cell cycle progression. This way, Rad9 serves as an adaptor protein that fosters the interactions between key proteins that serve in the cell cycle control system to ensure the integrity of DNA before mitosis phase occurs. Role/interactions in DNA repair Cells have a number of DNA repair mechanisms that are frequently active as a result of various exposures to radiation, carcinogens, and reactive oxygen species in the body. In such events, oxidative base lesions of DNA nucleotides are common. Rad-9 has been implicated with most DNA repair mechanisms, and plays a key role as it interacts with multiple proteins within each pathway. For instance, Rad-9 acts as an activator for many vital proteins that are responsible for the base excision repair process. First, Rad-9 interacts with many DNA glycosylases that are responsible for repairing specific nucleotide lesions, e.g. Human NEIL1 DNA glycosylase, thymine DNA glycosylase, 8-oxoguanine DNA glycosylase (OGG1). Furthermore, Rad-9, either as a free floating protein or part of the 9-1-1 complex, interacts with the rest of the proteins that are part of the base excision repair process, guiding its progression through the various stages. It has known interactions with apurinic/apyrimidinic endonuclease 1 (APE1), polymerase β (Polβ), Flap endonuclease 1 (FEN1), and DNA ligase I. During DNA replication, a number of point mutations can occur, where nucleotides are deleted, inserted, or mismatched, all of which must be repaired before mitosis occurs. Rad-9 has been implicated to have a number of key interactions with mismatch repair protein complexes MLH1, MSH2, MSH3, and MSH6. Also, it has known interaction in the following repair mechanisms: nucleotide excision repair (NER), DNA interstrand cross-links resistance, and homologous recombination (HR) Role in apoptosis Normally, cells possess many checkpoints and repair mechanisms to fix the DNA and regain proper function before mitosis. However, when DNA damage is too extensive for the repair mechanism, cells can activate apoptosis to trigger cellular death. During such an event, Rad9 is overexpressed and translocated into the mitochondria. The BH3 motif, located in the N-terminal of