Dynamics of the DNA repair proteins WRN and BLM in the nucleoplasm and nucleoli

Abstract

We have investigated the mobility of two EGFP-tagged DNA repair proteins, WRN and BLM. In particular, we focused on the dynamics in two locations, the nucleoli and the nucleoplasm. We found that both WRN and BLM use a “DNA-scanning” mechanism, with rapid binding–unbinding to DNA resulting in effective diffusion. In the nucleoplasm WRN and BLM have effective diffusion coefficients of 1.62 and 1.34 μm2/s, respectively. Like wise, the dynamics in the nucleoli are also best described by effective diffusion, but with diffusion coefficients a factor of ten lower than in the nucleoplasm. From this large reduction in diffusion coefficient we were able to classify WRN and BLM as DNA damage scanners. In addition to WRN and BLM we also classified other DNA damage proteins and found they all fall into one of two categories. Either they are scanners, similar to WRN and BLM, with very low diffusion coefficients, suggesting a scanning mechanism, or they are almost freely diffusing, suggesting that they interact with DNA only after initiation of a DNA damage response.

Identifying novel SMYD3 interactors on the trail of cancer hallmarks

“…SMYD3 modulates DNA damage response by interacting with ATM, BRCA2, CHK2 [28] , and possibly BLM, as reported here. After initiation of a DNA damage response, BLM binds to the DNA, potentially acting as a scanner of residual DNA damage [108] , [109] . SMYD3 interaction with p130 may also be included in this functional context since p130 is a key regulator of cell division entry and p53-mediated DNA damage response [76] , [110] .…”

WRN helicase is a synthetic lethal target in microsatellite unstable cancers

“…8b–d) and less nucleoplasmic staining in MSS cells. Since WRN has been demonstrated to respond to DNA damage by disseminating from the nucleolus towards the nucleoplasm 20 , these data suggest WRN is recruited to maintain genomic integrity in MSI cells.…”

WRN Helicase is a Synthetic Lethal Target in Microsatellite Unstable Cancers

“…WRN has been reported to respond to stress upon DNA damage by disseminating from the nucleolus towards the DNA in the nucleoplasm 38,39 the clinical manifestations of this syndrome require decades to emerge, suggesting that the therapeutic benefits would likely greatly outweigh these risks. Therefore, inhibitors of WRN could emerge as potent new therapy for this large and deadly class of human cancer.…”