Abstract
DNA polymerase β (Polβ) stability is tightly regulated by specific binding partners that prevent its proteasomal degradation. Ubiquitin (Ub) chains, differing in their structural arrangements (topology), contribute to distinct cellular functions. To investigate Polβ ubiquitylation, we utilized CRISPR/Cas9-modified cell lines expressing endogenous, mClover-tagged Polβ. Our results reveal that Polβ is primarily modified with ubiquitin chains linked through lysine residues 27 [Ub(K27)] and 29 [Ub(K29)]. We further observed that Ub(K27) and Ub(K29) chains affect the utilization of ubiquitin chains linked via lysine residues 6 [Ub(K6)] and 48 [Ub(K48)] during Polβ ubiquitylation. The ubiquitin ligase TRIP12 preferentially attaches Ub(K27) and Ub(K29) chains to Polβ. While Polβ ubiquitylation with Ub(K27) appears to have a non-degradative role, mixed ubiquitin chains and Ub(K48) chains trigger Polβ degradation. Following DNA damage, Polβ and XRCC1 translocate from the cytosol to the nucleus, while ubiquitylated Polβ relocates from the chromatin to the cytosol. This translocation of Polβ, modified with Ub(K27) chains, promotes the dissociation of the Polβ/XRCC1 complex within chromatin, and oxidative stress enhances their association in the cytosol. These findings demonstrate that atypical ubiquitin chain modifications play crucial roles in DNA repair and the DNA damage response, underscoring the unexpected importance of these chain topologies in maintaining genome integrity.
Since 2004, UT Health San Antonio, Greehey Children’s Cancer Research Institute’s (Greehey CCRI) mission has been to advance scientific knowledge relevant to childhood cancer, contribute to the understanding of its causes, and accelerate the translation of knowledge into novel therapies. Through the discovery, development, and dissemination of new scientific knowledge, Greehey CCRI strives to have a national and global impact on childhood cancer. Our mission consists of three key areas: research, clinical, and education.
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