Skip to main content

DEWAR Lab

Topoisomerase II poisons inhibit vertebrate DNA replication through distinct mechanisms

AUTHORS

Van Ravenstein SXSabrina X , Mehta KPKavi P , Kavlashvili TTamar , Byl JAWJo Ann W , Zhao RRunxiang , Osheroff NNeil , Cortez DDavid , Dewar JMJames M . The EMBO journal. 2022 5 16; 41(12). e110632

ABSTRACT

Topoisomerase II (TOP2) unlinks chromosomes during vertebrate DNA replication. TOP2 “poisons” are widely used chemotherapeutics that stabilize TOP2 complexes on DNA, leading to cytotoxic DNA breaks. However, it is unclear how these drugs affect DNA replication, which is a major target of TOP2 poisons. Using Xenopus egg extracts, we show that the TOP2 poisons etoposide and doxorubicin both inhibit DNA replication through different mechanisms. Etoposide induces TOP2-dependent DNA breaks and TOP2-dependent fork stalling by trapping TOP2 behind replication forks. In contrast, doxorubicin does not lead to appreciable break formation and instead intercalates into parental DNA to stall replication forks independently of TOP2. In human cells, etoposide stalls forks in a TOP2-dependent manner, while doxorubicin stalls forks independently of TOP2. However, both drugs exhibit TOP2-dependent cytotoxicity. Thus, etoposide and doxorubicin inhibit DNA replication through distinct mechanisms despite shared genetic requirements for cytotoxicity.