부산대학교 도서관

The eukaryotic replisome is rapidly disassembled during DNA replication termination. In metazoa, the cullin‐RING ubiquitin ligase CUL‐2LRR‐1 drives ubiquitylation of the CMG helicase, leading to replisome disassembly by the p97/CDC‐48 "unfoldase". Here, we combine in vitro reconstitution with in vivo studies in Caenorhabditis elegans embryos, to show that the replisome‐associated TIMELESS‐TIPIN complex is required for CUL‐2LRR‐1 recruitment and efficient CMG helicase ubiquitylation. Aided by TIMELESS‐TIPIN, CUL‐2LRR‐1 directs a suite of ubiquitylation enzymes to ubiquitylate the MCM‐7 subunit of CMG. Subsequently, the UBXN‐3 adaptor protein directly stimulates the disassembly of ubiquitylated CMG by CDC‐48_UFD‐1_NPL‐4. We show that UBXN‐3 is important in vivo for replisome disassembly in the absence of TIMELESS‐TIPIN. Correspondingly, co‐depletion of UBXN‐3 and TIMELESS causes profound synthetic lethality. Since the human orthologue of UBXN‐3, FAF1, is a candidate tumour suppressor, these findings suggest that manipulation of CMG disassembly might be applicable to future strategies for treating human cancer. Synopsis: Different factors contribute to ubiquitylation‐mediated DNA replication termination in different eukaryotic systems. Here, replisome disassembly in Caenorhabditis elegans is found to be stimulated by the replisome‐associated TIMELESS‐TIPIN complex and the p97/CDC‐48 unfoldase adaptor UBXN‐3. Caenorhabditis elegans TIM‐1_TIPN‐1 stimulates CMG helicase ubiquitylation by the CUL‐2_LRR‐1 ligase in a reconstituted in vitro system.The TIM‐1_TIPN‐1 complex is important for the association of CUL‐2_LRR‐1 with the CMG helicase.The TIM‐1_TIPN‐1 complex stimulates CMG ubiquitylation during replication termination in vivo in the C. elegans early embryo.UBXN‐3 stimulates the disassembly of ubiquitylated CMG by CDC‐48_UFD‐1_NPL‐4 in vitro and in vivo. [ABSTRACT FROM AUTHOR]