title: Ubiquitin-dependent recruitment of the Bloom syndrome helicase upon replication stress is required to suppress homologous recombination.
abstract: Limiting the levels of homologous recombination (HR) that occur at sites of DNA damage is a major role of BLM helicase. However, very little is known about the mechanisms dictating its relocalization to these sites. Here, we demonstrate that the ubiquitin/SUMO-dependent DNA damage response (UbS-DDR), controlled by the E3 ligases RNF8/RNF168, triggers BLM recruitment to sites of replication fork stalling via ubiquitylation in the N-terminal region of BLM and subsequent BLM binding to the ubiquitin-interacting motifs of RAP80. Furthermore, we show that this mechanism of BLM relocalization is essential for BLM's ability to suppress excessive/uncontrolled HR at stalled replication forks. Unexpectedly, we also uncovered a requirement for RNF8-dependent ubiquitylation of BLM and PML for maintaining the integrity of PML-associated nuclear bodies and as a consequence the localization of BLM to these structures. Lastly, we identified a novel role for RAP80 in preventing proteasomal degradation of BLM in unstressed cells. Taken together, these data highlight an important biochemical link between the UbS-DDR and BLM-dependent pathways involved in maintaining genome stability.
authors.affiliation: National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi, India.
authors.forename: Shweta
authors.initials: S
authors.lastname: Tikoo
authors.forename: Vinoth
authors.initials: V
authors.lastname: Madhavan
authors.forename: Mansoor
authors.initials: M
authors.lastname: Hussain
authors.forename: Edward S
authors.initials: ES
authors.lastname: Miller
authors.forename: Prateek
authors.initials: P
authors.lastname: Arora
authors.forename: Anastasia
authors.initials: A
authors.lastname: Zlatanou
authors.forename: Priyanka
authors.initials: P
authors.lastname: Modi
authors.forename: Kelly
authors.initials: K
authors.lastname: Townsend
authors.forename: Grant S
authors.initials: GS
authors.lastname: Stewart
authors.forename: Sagar
authors.initials: S
authors.lastname: Sengupta
mesh_terms: D000818:Animals; D002460:Cell Line; D004249:DNA Damage; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D042822:Genomic Instability / Q000502:physiology*; D059765:Homologous Recombination / Q000502:physiology*; D006801:Humans; D046988:Proteasome Endopeptidase Complex / Q000235:genetics / Q000378:metabolism; D059748:Proteolysis; D053484:RecQ Helicases / Q000235:genetics / Q000378:metabolism*; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism; D054875:Ubiquitination / Q000502:physiology*
chemical_list: D004268:DNA-Binding Proteins; C486521:RNF8 protein, human; C535210:RNF168 protein, human; D044767:Ubiquitin-Protein Ligases; D046988:Proteasome Endopeptidase Complex; C097151:Bloom syndrome protein; D053484:RecQ Helicases