A DNA-binding domain in the C-terminal region of Cdt2 enhances the DNA synthesis-coupled CRL4Cdt2 ubiquitin ligase activity for Cdt1

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

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.

Preparation for DNA replication: the key to a successful S phase

Successful genome duplication is required for cell proliferation and demands extraordinary precision and accuracy. The mechanisms by which cells enter, progress through, and exit S phase are intense areas of focus in the cell cycle and genome stability fields. Key molecular events in the G1 phase of the cell division cycle, especially origin licensing, are essential for pre-establishing conditions for efficient DNA replication during the subsequent S phase. If G1 events are poorly regulated or disordered, then DNA replication can be compromised leading to genome instability, a hallmark of tumorigenesis. Upon entry into S phase, coordinated origin firing and replication progression ensure complete, timely, and precise chromosome replication. Both G1 and S phase progressions are controlled by master cell cycle protein kinases and ubiquitin ligases that govern the activity and abundance of DNA replication factors. In this short review, we describe current understanding and recent developments related to G1 progression and S phase entrance and exit with a particular focus on origin licensing regulation in vertebrates.