The Role of HUWE1 in DNA replication and genome stability in multiple myeloma

Knockdown of HUWE1 using shRNA technology demonstrated significantlyreduced cellular proliferation compared to the control which was underpinned bya S phase arrest. Replication proteins were identified as a novel substrate ofHUWE1, which was found to catalyse the polyubiquitination of the replicationprotein. Further investigation found that this HUWE1-mediated ubiquitinationwas essential for loading of these proteins to sites of DNA damage induced byreplicative stress and ultimately resulted in a DNA damage repair defect. </p><p>Another area of this studyfocused on delineating the functional consequences of clinically relevant HUWE1mutations which are observed in approximately 5% of MM patients.

Patients witha HUWE1 mutation were observed to have significantly higher number ofco-occurrent non-synonymous and somatic mutations. Analysis of a panel of MMcell lines with wild-type or mutant HUWE1, identified a similar phenotype inwhich HUWE1 mutant cell lines exhibited higher mutation rates as determined bythe PIG-A gene mutation assay and increased incidence of micronuclei formation,two characteristics indicative of genomic instability.

This loss of genomestability was determined to be underpinned by a dampened DNA repair response. </p><p>This work outlines a clear rolefor HUWE1 in genome stability and highlights that exploitation of thereplication stress response may represent a therapeutic vulnerability for MM patientswith a HUWE1 mutation.</p><br>