Design of a System for Monitoring Ubiquitination Activities of E2 Enzymes Using Engineered RING Finger Proteins.

Ubiquitination is a sequential cascade consisting of ubiquitin-activating (E1), ubiquitin-conjugating (E2), and ubiquitin-ligating (E3) enzymes. It controls numerous processes such as protein degradation, DNA repair, and signal transduction pathways. E2 enzymes are associated with a variety of diseases such as leukemia, breast cancer, lung cancer, and colorectal cancer. To date, the monitoring of E2 activity for cancer diagnosis is challenging due to its intricate cascade reaction. To surmount this hurdle, we have recently developed a novel strategy for monitoring E2 activities. Here, we describe the concise machinery of ubiquitination with artificial RING finger proteins (ARFs) functioning as E3 enzymes. This machinery enables the simplified monitoring of E2 activities. Furthermore, our system combines a signal accumulation ion-sensitive field-effect transistor biosensor with ARFs, allowing for real-time monitoring of the pathological conditions of cancer cells. The present methodology may lead to novel diagnostic techniques for cancers.