REV7 Acts Independently of Polymerase ζ to Maintain Genome Stability During Development
Authors: Lara Maggs; Mitch McVey
Affiliation: Tufts University, Medford, MA
Keywords: j. DNA repair; i. DNA replication
Genome stability is of vital importance during an organism’s life. Without appropriate and timely DNA damage response, development is misregulated or entirely disrupted, leading to unhealthy or non-viable offspring. Recent mammalian work indicates REV7 plays a significant role in DNA damage response. REV7 is a component of Polymerase ζ, used in translesion DNA synthesis (TLS), as well as influences double-strand break (DSB) repair pathway choice as a member of the shieldin complex. REV7, a HORMA domain protein, employs its stereotypical safety belt region to interact with other proteins in these complexes.
As such, we wanted to investigate whether REV7 has functions beyond TLS in Drosophila. We used mutant stocks in which the REV7 coding sequence is interrupted by a piggyBac transposable element to characterize phenotypes during normal development and after treatment with exogenous DNA damaging agents. Our studies indicate REV7 loss impairs development to adulthood, decreases hatching rate, and produces abnormal eggshells. The sub-Mendelian ratio of homozygous flies indicates the importance of REV7 in early development. This conclusion is further bolstered by decreased hatching rates, reinforcing the significance of REV7 during development in response to innate endogenous damage. Imperative to successful development is the eggshell, a sophisticated proteinaceous structure composed of chorion, produced en masse via gene amplification. rev7 mutant females produce eggs with partially translucent eggshells. This phenotype has been observed in other DSB repair mutants and is attributed to persistent damage resulting from replication fork collisions during amplification at two chorion loci. Data collected from REV3, Pol ζ’s catalytic subunit, mutants do not echo REV7 loss, suggesting REV7 is acting independently of Pol ζ.
Our findings are consistent with REV7 acting in additional non-TLS roles. We are currently working to identify protein partners that interact with REV7 in support of genome stability. These investigations will provide additional insight into the mechanism(s) by which Drosophila REV7 promotes genome stability in the developmental context.