Rev3, the catalytic subunit of Polζ, is required for maintaining fragile site stability in human cells

Abstract

It has been long speculated that mammalian Rev3 plays an important, yet unknown role(s) during mammalian development, as deletion of Rev3 causes embryonic lethality in mice, whereas no other translesion DNA synthesis polymerases studied to date are required for mouse embryo development. Here, we report that both subunits of Polζ (Rev3 and Rev7) show an unexpected increase in expression during G2/M phase, but they localize independently in mitotic cells. Experimental depletion of Rev3 results in a significant increase in anaphase bridges, chromosomal breaks/gaps and common fragile site (CFS) expression, whereas Rev7 depletion primarily causes lagging chromosome defect with no sign of CFS expression. The genomic instability induced by Rev3 depletion seems to be related to replication stress, as it is further enhanced on aphidicolin treatment and results in increased metaphase-specific Fanconi anemia complementation group D type 2 (FANCD2) foci formation, as well as FANCD2-positive anaphase bridges. Indeed, a long-term depletion of Rev3 in cultured human cells results in massive genomic instability and severe cell cycle arrest. The aforementioned observations collectively support a notion that Rev3 is required for the efficient replication of CFSs during G2/M phase, and that the resulting fragile site instability in Rev3 knockout mice may trigger cell death during embryonic development.

TopBP1-mediated DNA processing during mitosis

“…83,84 Similarly the level of Rev3, which is the catalytic subunit of the TLS polymerase zeta peaks in mitosis. 85,86 Moreover, Rev3 localizes to chromatin at this stage of the cell cycle and Rev3 has a suggested role for replication of CFS in G2/M in a manner that is independent of the Rev7 subunit of the polymerase zeta complex. 86 Replication stress-induced 53BP1 nuclear bodies in G1…”

Rev7/Mad2B plays a critical role in the assembly of a functional mitotic spindle

“…28 This led us to suspect that Rev7 plays a role in mitosis distinct from its TLS function. This is in agreement with a previous report that Rev7 interacts with a RAN GTPase, 21 an essential component of a bipolar spindle formation, 25,26 thereby having a possible role in the spindle formation.…”

Interaction between gene repair and mobile elements-induced activity systems after low-dose irradiation

“…[A1]) has the defect in the gene mus205 (allele A1) involving in post-replication repair on the mechanism of homologous recombination (Kane et al 2012), in the repair of alkylation damage, excision repair of pyrimidine dimers and photorepair (Harris and Boyd 1993), homolog of mammal and human REV3L gene (Bhat et al 2013); stock mus304 (genotype:…”