Lack of RNase H2 activity rescues HU-sensitivity of WEE1 deficient plants.

Because of their sessile lifestyle, plants have developed extensive mechanisms to safeguard their genetic information from one generation to the next. The WEE1 kinase is one of the guardians of genome integrity, being important during S-phase progression under replication stress. Knock-out plants for WEE1 (WEE1(KO)) show a hypersensitive response when grown on replication-inhibiting drugs. Recently, we reported the identification of a mutant in the RNase H2A gene that could partially complement this replication phenotype. Here, we present the identification of a second member of the RNase H2 complex, RNase H2B, being able to complement the root growth phenotype of WEE1(KO) plants. We additionally show that deletion of a conserved domain in RNase H2B leads to loss of interaction with the RNase H2C subunit, likely explaining the loss of activity of the RNase H2 complex.