We have shown previously that the process of replication machinery (replisome) disassembly at the termination of DNA replication forks in the S-phase is driven through polyubiquitylation of one of the replicative helicase subunits (Mcm7) by Cul2LRR1 ubiquitin ligase. Interestingly, upon inhibition of this pathway in Caenorhabditis elegans embryos, the replisomes retained on chromatin were unloaded in the subsequent mitosis. Here, we show that this mitotic replisome disassembly pathway exists in Xenopus laevis egg extract and we determine the first elements of its regulation. The mitotic disassembly pathway depends on the formation of K6- and K63-linked ubiquitin chains on Mcm7 by TRAIP ubiquitin ligase and the activity of p97/VCP protein segregase. Unlike in lower eukaryotes, however, it does not require SUMO modifications. Importantly, we also show that this process can remove all replisomes from mitotic chromatin, including stalled ones, which indicates a wide application for this pathway over being just a “backup” for terminated replisomes. Finally, we characterise the composition of the replisome retained on chromatin until mitosis.

Objective Heat shock proteins are molecules rapidly produced under conditions of environmental stress, and involve in protecting the cells structural integrity and function. Osteoarthritis (OA) is a chronic destructive disorder of the joints manifested by the ongoing deterioration and loss of articular cartilage. The present study aimed to analyze circulating and synovial heat shock protein (Hsp70) values in knee osteoarthritis patients and healthy controls and to determine their relationship with the radiographic grading of the severity of knee OA. Design Seventy-two subjects with knee OA and 30 control participants were recruited. Circulating and joint fluid Hsp70 values were quantified by commercially available enzyme-linked immunosorbent assay. Results Circulating Hsp70 was markedly higher in knee OA patients compared with that of healthy volunteers ( P = 0.01). Correspondingly, synovial fluid Hsp70 was 3-fold greater than paired circulating Hsp70 samples ( P < 0.001). Further analysis revealed that circulating and joint fluid Hsp70 values were significantly related with the radiographic severity of knee OA ( r = 0.413, P < 0.001 and r = 0.658, P < 0.001, respectively). Subsequently, circulating Hsp70 value was directly associated with joint fluid Hsp70 value ( r = 0.704, P < 0.001). Conclusions Circulating and synovial Hsp70 levels were positively correlated with the radiographic severity of knee OA. Hsp70 could represent a potential biochemical marker for predicting the severity and may play a fundamental part in the pathogenic mechanism of knee OA.