PCNA-Ub polyubiquitination inhibits cell proliferation and induces cell-cycle checkpoints

Abstract

In response to replication-blocking lesions, proliferating cell nuclear antigen (PCNA) can be sequentially ubiquitinated at the K164 residue leading to 2 modes of DNA-damage tolerance, namely translesion DNA synthesis (TLS) and error-free lesion bypass. Ectopic expression of PCNA fused with ubiquitin (Ub) lacking the 2 C-terminal Gly residues resembles PCNA monoubiquitination-mediated TLS. However, if the fused Ub contains C-terminal Gly residues, it is further polyubiquitinated and inhibits cell proliferation. Unexpectedly, the polyubiquitination chain does not require any surface Lys residues and is likely to be head-to-tail linked. Such PCNA polyubiquitination interferes with replication, arrests cells at the S-phase and activates the p53 checkpoint pathway. The above cell-cycle arrest is reversible in an ATR-dependent manner, as simultaneous inhibition of ATR, but not ATM, induces apoptosis. Since ectopic expression of PCNA-Ub also induces double-strand breaks that colocalize with single-stranded DNA, we infer that this non-canonical PCNA poly-Ub chain serves as a signal to activate ATR checkpoint and recruit doublestrand-break repair apparatus.

Methylation of UHRF1 by SET7 is essential for DNA double-strand break repair

“…The Rad6/Rad18 complex catalyzes monoubiquitination of PCNA at K164; these results in replacement of replicative polymerase with an alternative DNA polymerase, promoting the error-prone repair pathway, translesion synthesis (45). In contrast, polyubiquitination of PCNA at K164 has been known to promote ‘error-free repair’ to DNA damage (5,46), but this pathway is currently poorly defined (6). The E3 ligases, HLTF and SHPRH, known to catalyze polyubiquitination of PCNA, are not sufficient for polyubiquitination of PCNA, since Hltf-/- and Shprh-/- double-knockout mouse embryonic fibroblasts seem to display some residual PCNA polyubiquitylation (47).…”

KAP1 phosphorylation promotes the survival of neural stem cells after ischemia/reperfusion by maintaining the stability of PCNA

“…PCNA can bind to different replication-related proteins to coordinate the DNA replication process [26,[46][47][48]. PCNA also acts as a functional conversion factor, interacts with various cytokines through different regulatory modes, and participates in many important cellular events, including DNA damage repairment and refinement, cell cycle regulation, and apoptosis [46,[49][50][51]. As an indicator of cell proliferation, PCNA correlates with the occurrence and development of diseases linked to cell proliferation [51][52][53].…”

KAP1 Phosphorylation Promotes the Survival of Neural Stem Cells after Ischemia/Reperfusion by Maintaining the Stability of PCNA

“…PCNA can bind to different replication-related proteins to coordinate the DNA replication process [26,[40][41][42] . PCNA also acts as a functional conversion factor, interacts with a variety of cytokines through different regulatory modes, and participates in many important cellular events including DNA damage repairment and re nement, cell cycle regulation, and apoptosis [40,[43][44][45] . As an indicator of cell proliferation, PCNA correlates with the occurrence and development of diseases linked to cell proliferation [45][46][47] .…”

“…PCNA poly-ubiquitination has been shown to inhibit cell proliferation and regulate cell differentiation, apoptosis, and other processes [44,53] . The decreased expression of PCNA induced by cerebral I/R could be reversed by the p-KAP1mimic, possibly due to the altered stability of PCNA.…”