SPECIALIZED POLYMERASE IOTA MAINTAINS GENOMIC STABILITY BY PREVENTING EXCESS PRIMPOL-DRIVEN DNA REPLICATION

SOFIA VENERUS ARBILLA; MANSILLA, SABRINA FLORENCIA; BERTOLIN AGOSTINA; SEBASTIÁN OMAR SIRI; DE LA VEGA, MARÍA BELÉN; WIESMÜLLER, LISA; VANESA GOTTIFREDI

Mendoza

Congreso; Sociedad Argentina de Investigacion en bioquimica y biologia molecular; 2022

SAIB

DNAreplication must adapt to imperfect templates which arefrequent even in genotoxin-freeconditions. Replicative polymerases come to ahalt when encountering damagedDNA, causing the activation of a signalingnetwork known as DDR (DNA DamageResponse). DDR includes mechanisms of DNAdamage tolerance, such as TLS(Translesion DNA Synthesis), which engagesspecialized polymerases(TLS-Pols) into the replication of imperfect DNAtemplates. There is asurprising redundancy among TLS-Pols. To study thedifferential contribution ofthese polymerases to the DDR, we explored thelevels of replication stresstriggered by the downregulation of differentspecialized DNA polymerases underCDDP-treated conditions. As expected,replication stress increased afterdepletion of almost all TLS-Pols, with thesurprising exception of  polymerase Iota (Pol i), whosedownregulation caused reduced replication stress, faster DNAreplication rates,increased frequency of origin firing and diminished S phaselength. Such aunique contribution of Pol i to the optimization oftheDNA Damage Response was linked to the capacity of Pol i tolimit nascent DNA elongation under both stressed and unstressedconditions. Inthe absence of Pol i, the faster DNAreplication rates diminishedthe length of S phase with no apparent upregulationof replication stresssignals. Yet, these at first sight harmless effects on theDNA replicationdynamics were accompanied by augmented levels ofunder-replicated DNA in Mphase, chromosome instability and micronucleiaccumulation. M phaseabnormalities were rescued when the excess nascent DNAelongation triggered byPol i depletion was restrainedby simultaneouslydepleting the repriming polymerase PrimPol. Hence, our resultsreveal that Pol icontributes to the maintenance of genomic stability bypreventing excessPrimPol-driven DNA replication. In the future, we plan tocharacterize themechanism by which Pol i contributes to the DDR bytestingthe relevance of each of its domains;aswell as which PrimPol domains are critical for driving genomic instabilityinPol i deficientbackgrounds