Unique E2-binding specificity of artificial RING fingers in cancer cells

Abstract

Ubiquitin (Ub)-conjugating enzymes (E2s) are involved in various pathways for Ub transfer and deubiquitinating activities. These enzymes are associated with cancers such as breast cancer which is the second deadliest type of malignancy among women. Here, we revealed the unique E2-binding property and the auto-ubiquitination of artificial RING fingers (ARFs). Circular dichroism spectra showed the characteristic structures of ARFs. The proline, lysine, leucine, threonine and cysteine (PKLTC) sequence of ARF was important for E2-recognition and its mutations induced obvious changes in the E2-binding specificity and the auto-ubiquitination activity of ARF. The ARF mutants were applicable to detection of most of E2 activities. Furthermore, adding the ARF mutant C35A to cancer cells promoted its auto-ubiquitination, leading to the preferential detection of E2 UbcH5b activity. The present work opens up a new avenue for investigating intracellular E2 activities for the fatal diseases.