New insights into the formation and resolution of ultra-fine anaphase bridges

Recent data indicate an unexpected requirement for proteins that were hitherto considered to be dedicated to DNA repair to facilitate the faithful disjunction of sister chromatids in anaphase. These include the Bloom's syndrome gene product, BLM and its partners, as well as a number of proteins that are important for preventing Fanconi anemia (FA) in man. As part of an analysis of the roles of these proteins in mitosis, we identified a novel class of anaphase bridge structure, called an ultra-fine anaphase bridge (UFB). These UFBs are also defined by the presence of a SNF2 family protein called PICH. In this review, we will discuss the possible sources of UFBs, and how the BLM, PICH and FA proteins might serve to process these structures in order to maintain genome stability.

► Human cells contain ultra-fine DNA bridges in anaphase (UFBs) that cannot be stained with dyes.
► DNA repair proteins, such as the Bloom's syndrome helicase, BLM, and a translocase, PICH, bind UFBs.
► Cells lacking BLM or PICH contain more UFBs and these cannot be resolved in anaphase.
► Most UFBs originate from specific loci; either centromeres or fragile sites.
► A DNA damage response is triggered in G1 phase when the preceding anaphase is defective.