CRL4Cdt2 Ubiquitin Ligase, A Genome Caretaker Controlled by Cdt2 Binding to PCNA and DNA.

Muadz Ahmad Mazian,Kumpei Yamanishi,Menega Ganasen,Hideo Nishitani,Mohd Zulhilmi Abdul Rahman

doi:10.3390/genes13020266

Abstract

The ubiquitin ligase CRL4Cdt2 plays a vital role in preserving genomic integrity by regulating essential proteins during S phase and after DNA damage. Deregulation of CRL4Cdt2 during the cell cycle can cause DNA re-replication, which correlates with malignant transformation and tumor growth. CRL4Cdt2 regulates a broad spectrum of cell cycle substrates for ubiquitination and proteolysis, including Cdc10-dependent transcript 1 or Chromatin licensing and DNA replication factor 1 (Cdt1), histone H4K20 mono-methyltransferase (Set8) and cyclin-dependent kinase inhibitor 1 (p21), which regulate DNA replication. However, the mechanism it operates via its substrate receptor, Cdc10-dependent transcript 2 (Cdt2), is not fully understood. This review describes the essential features of the N-terminal and C-terminal parts of Cdt2 that regulate CRL4 ubiquitination activity, including the substrate recognition domain, intrinsically disordered region (IDR), phosphorylation sites, the PCNA-interacting protein-box (PIP) box motif and the DNA binding domain. Drugs targeting these specific domains of Cdt2 could have potential for the treatment of cancer.

Highlights

Chromatin licensing and DNA replication factor 1 (Cdt1) cooperates with cell division cycle 6 (Cdc6) to aid in loading the hexameric minichromosome maintenance (MCM2-7) helicase complex at sites that bind origin recognition complex (ORC). This results in the formation of a prereplicative complex at origins of replication, which is essential for the initiation of DNA replication
The BPB domain interacts with the N-terminal part of CUL4, whereas the BPA and BPC domains interact with their substrate receptors, referred to as DNA damage binding protein 1 (DDB1)-CUL4 associated factors (DCAFs), such as Cdc10-dependent transcript 2 (Cdt2) (Figure 1A) [7,13]
During S phase and upon DNA damage, proliferating cell nuclear antigen (PCNA) is loaded onto chromatin, where it serves as a platform for proteins involved in DNA replication, DNA repair and chromatin metabolism to interact with each other [23,24]

Summary

Introduction

The third principle of cell theory states that a cell arises from a pre-existing living cell through cell division [1]. Initiation of DNA replication in S phase activates the proliferating cell nuclear antigen (PCNA)-dependent proteolysis of licensing factor, Cdt by CRL4Cdt, a Cullin RING E3 ubiquitin ligase, to inhibit re-replication. Cdt cooperates with cell division cycle 6 (Cdc6) to aid in loading the hexameric minichromosome maintenance (MCM2-7) helicase complex at sites that bind origin recognition complex (ORC). This results in the formation of a prereplicative complex (pre-RC) at origins of replication, which is essential for the initiation of DNA replication. The ubiquitin-mediated proteolytic degradation of Cdt, Set and p21 by the CRL4 (DDB1-CUL4-Rbx1)-Cdt protein complex, hereafter referred to as CRL4Cdt, is vital to ensure once-per-cell-cycle DNA replication, as depletion of Cdt induces massive re-replication [13]. The Cterminal portion of CUL4 conjugates with NEDD8 and is linked to the binding of the RING domain protein Rbx, to which E2 is recruited [13]

Cdc10-Dependent Transcript-2, Cdt2

Overview of Substrate Recognition by CRL4Cdt2 (PCNADNA-Dependent)

PIP Box at the C-Terminal End of Cdt2

Phosphorylation of the C-Terminal of Cdt2

DNA Binding Domain in the C-Terminal Region

Conclusions and Perspective