Epidermal Growth Factor Receptor Protects Proliferating Cell Nuclear Antigen from Cullin 4A Protein-mediated Proteolysis

Abstract

Background: Phosphorylation of the proliferating protein PCNA through the signaling of receptor tyrosine kinases (RTKs) protects it from ubiquitylation-mediated degraded on the chromatin. Results: The ubiquitylation enzyme CUL4A is responsible for PCNA degradation in the absence of phosphorylation. Conclusion: Phosphorylation of PCNA stabilizes PCNA by blocking interaction between PCNA and CUL4A. Significance: This may help sensitize cancer cells to therapeutic agents targeting RTKs.

14‐3‐3ζ Reduces DNA Damage by Interacting With and Stabilizing Proliferating Cell Nuclear Antigen

“…Mono‐ and polyubiquitinations mediated by Rad6‐Rad18 and Ubc13/Mms2/Rad5 complexes on the K164 residue have been generally associated to the switches between different modes of DNA replication and repair [Prakash et al, ; Washington et al, ], whereas controversies exist regarding the role of the ubiquitination at the same K164 residue mediated by the cullin‐RING family member CRL4 Cdt2 . Indeed, It has been reported to be involved either in translesion DNA synthesis [Terai et al, ], or in the proteasomal degradation of PCNA [Lo et al, ]. Further investigation aiming to confirm the regulatory role of 14‐3‐3ζ in the ubiquitination of PCNA and to elucidate its precise mechanisms should take account of all these facts.…”

“…KEY WORDS: 14-3-3z; PCNA; PROTEIN-PROTEIN INTERACTION; STABILITY; DNA DAMAGE P roliferating cell nuclear antigen (PCNA) is a so-called DNA sliding clamp protein which plays a critical role in the replication of the genome. During DNA replication, by forming a ring-shaped homotrimer that encircles, and slides along the doublestranded DNA, PCNA serves as a molecular platform that coordinates the complex interacting network around the DNA polymerase at the replication fork and enhances the processivity of the latter by tethering it to DNA [Maga and Hubscher, 2003;Qi and Martinez, 2003;Essers et al, 2005;Lo et al, 2012]. During DNA replication, the advance of the replication fork is often blocked by the lesions in DNA templates.…”

“…Interestingly, besides its role in the control of the switch between different modes of DNA replication and repair, recent studies suggested that the ubiquitination of PCNA might also be involved in its proteasomal degradation and thereby plays a role in the stability of this protein. Lo et al reported that in human cells, polyubiquitination on Lys164 mediated by the E3 ligase Cullin 4A could trigger the proteasomal degradation of PCNA [Lo et al, 2012]. Thus, mono-and poly-ubiquitination mediated by SHORT HAIRPIN RNAs (shRNAs) Recombinant lentivirus carrying 14-3-3z-knockdown shRNA (ACGGTTCACATTCCATTAT) [Li et al, 2008] was produced with LV-3 (pGLVH1/GFP þ Puro) vector (GenePharma, Shanghai, China).…”

CBP and p300 acetylate PCNA to link its degradation with nucleotide excision repair synthesis

“…Later, phosphorylation at tyrosine 211 (Tyr211) by epidermal growth factor (EGF) receptor kinase (26), and c-Abl tyrosine kinase (27) were shown to regulate PCNA stability during DNA replication (28). The association with ERK8 kinase also influenced PCNA stability by regulating the interaction with MDM2, although no evidence that ERK8 could phosphorylate PCNA, was provided (29).…”

Readers of PCNA modifications

“…Mutation of Y211 to phenylalanine caused polyubiquitylation and proteasomal degradation of PCNA, while phosphorylation stabilised the protein. Intriguingly, although ubiquitylation was directed at K164 of PCNA, the modification did not involve the set of conjugation factors required for damage-induced ubiquitylation, but instead the Cullin 4-based ubiquitin ligase CRL4, which is known for assembly of K48-linked ubiquitin chains (Lo et al 2012). Phosphorylation at Y211 was found to interfere with the E3–PCNA interaction, thus explaining its stabilising effect.…”