However, BLM-TopBP1 binding is important for maintaining genome integrity, because in its absence cells display increased sister chromatid exchanges, replication origin firing and chromosomal aberrations.
Cells from Bloom's syndrome patients, that lack the RecQ helicase BLM, show defects in the response to replicative stress and contain a multitude of chromosomal aberrations, which primarily arise through excessive levels of homologous recombination.
Moreover, disruption of XRCC3 suppresses MMS and UV sensitivity and the MMS- and UV-induced chromosomal aberrations of blm cells, indicating that BLM acts downstream of XRCC3.