A DNA damage response screen identifies RHINO, a 9-1-1 and TopBP1 interacting protein required for ATR signaling

Area of Science:

• Molecular Biology
• Cell Biology
• Genetics

Background:

• The DNA damage response (DDR) is a complex network of cellular pathways that detect and repair DNA damage.
• Cell cycle arrest is a critical outcome of the DDR, preventing damaged cells from replicating.

Purpose of the Study:

• To identify novel proteins involved in the DDR pathway.
• To elucidate the role of uncharacterized proteins in ATR signaling and cell cycle arrest.

Main Methods:

• Screening for cells lacking DNA damage-induced cell cycle arrest.
• Investigating protein interactions at sites of DNA damage using molecular biology techniques.

Main Results:

• A screen identified cells lacking damage-induced cell cycle arrest, revealing a role for Fanconi anemia and homologous recombination proteins in ATR signaling.
• Three candidate DDR proteins, INTS7, CLOCK, and RHINO, were recruited to DNA damage sites.
• RHINO was found to bind independently to the Rad9-Rad1-Hus1 (9-1-1) complex and TopBP1.
• RHINO's recruitment to DNA damage sites by the 9-1-1 complex promotes Chk1 activation.

Conclusions:

• RHINO plays a critical role in ATR signaling by bridging the 9-1-1 complex and TopBP1.
• RHINO, the 9-1-1 complex, and TopBP1 function together to fully activate ATR, a key kinase in the DDR.
• These findings uncover a novel mechanism for ATR activation and highlight RHINO as a potential therapeutic target in DNA repair pathways.