PCNA antagonizes cohesin-dependent roles in genomic stability

Abstract

PCNA sliding clamp binds factors through which histone deposition, chromatin remodeling, and DNA repair are coupled to DNA replication. PCNA also directly binds Eco1/Ctf7 acetyltransferase, which in turn activates cohesins and establishes cohesion between nascent sister chromatids. While increased recruitment thus explains the mechanism through which elevated levels of chromatin-bound PCNA rescue eco1 mutant cell growth, the mechanism through which PCNA instead worsens cohesin mutant cell growth remains unknown. Possibilities include that elevated levels of long-lived chromatin-bound PCNA reduce either cohesin deposition onto DNA or cohesin acetylation. Instead, our results reveal that PCNA increases the levels of both chromatin-bound cohesin and cohesin acetylation. Beyond sister chromatid cohesion, PCNA also plays a critical role in genomic stability such that high levels of chromatin-bound PCNA elevate genotoxic sensitivities and recombination rates. At a relatively modest increase of chromatin-bound PCNA, however, fork stability and progression appear normal in wildtype cells. Our results reveal that even a moderate increase of PCNA indeed sensitizes cohesin mutant cells to DNA damaging agents and in a process that involves the DNA damage response kinase Mec1(ATR), but not Tel1(ATM). These and other findings suggest that PCNA mis-regulation results in genome instabilities that normally are resolved by cohesin. Elevating levels of chromatin-bound PCNA may thus help target cohesinopathic cells linked that are linked to cancer.

Hydroxyurea—The Good, the Bad and the Ugly

“…The most fundamental function of S-phase checkpoint activation is a delay in entry into mitosis [ 15 , 80 , 81 ]. In mammals, the kinases involved in the pathway work in a hierarchical way, beginning with ATR, which detects replication protein A (RPA)-coated DNA replication-associated lesions.…”

“…This stalled fork maintenance event is linked to the ATR/Chk1 pathway of inhibition of origin firing. Also, other proteins like cohesins have also been reported to play a role in maintaining fork stability by promoting their restart [ 81 , 93 , 94 , 95 , 96 ]. In the presence of low dNTP pools, new origin initiation can lead to accumulation of ssDNA that can further lead to DNA breaks and overall large-scale DNA damage.…”

“…Fork reversal is usually connected with higher levels of lagging and leading strand uncoupling in Rad53 mutants. Notably, exposure to HU leads to unloading of the PCNA protein ( Figure 3 B), mostly from the lagging strand [ 81 , 108 , 115 ]. It seems to be facilitated by S-phase checkpoint proteins, which supports the idea that, following HU-induced fork stalling, elongation of the lagging strand is inhibited [ 116 , 117 ].…”

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] .…”

G1-Cyclin2 (Cln2) promotes chromosome hypercondensation in eco1/ctf7 rad61 null cells during hyperthermic stress in Saccharomyces cerevisiae

“…Eco1/Ctf7 (human ESCO2/EFO2 and ESCO1/EFO1) is a highly conserved acetyltransferase that activates cohesin via acetylation of either Smc3 during S phase or Mcd1 (human RAD21) during G2/M in response to DNA damage ( Skibbens et al 1999 ; Tóth et al 1999 ; Bellows et al 2003 , Williams et al 2003 ; Rolef Ben-Shahar et al 2008 ; Unal et al 2008 ; Zhang, Shi, et al 2008 ; Heidinger-Pauli et al 2009 ). Eco1 is critical for sister chromatid cohesion, chromosome condensation, DNA damage repair, nucleolar integrity, and gene transcription ( Skibbens et al 1999 ; Ström et al 2004 , 2007 ; Unal et al 2004 , 2007 ; Heidinger-Pauli et al 2008 ; Gard et al 2009 ; Lu et al 2010 ; Alomer et al 2017 ; Billon et al 2017 ; Wu et al 2020 ; Zuilkoski and Skibbens 2020b ; Mfarej and Skibbens 2020a, 2022 ). Transcriptional dysregulations that arise in response to ESCO2 mutation in humans result in severe developmental abnormalities and intellectual disabilities termed Roberts syndrome (RBS) ( Schule et al 2005 ; Vega et al 2005 ; Gordillo et al 2008 ).…”