Human KIAA1018/FAN1 nuclease is a new mitotic substrate of APC/C^(Cdh1)

A recently identified protein, FAN1 (FANCD2-associated nuclease 1, previously known as KIAA1018), is a novel nuclease associated with monoubiquitinated FANCD2 that is required for cellular resistance against DNA interstrand crosslinking (ICL) agents. The mechanisms of FAN1 regulation have not yet been explored. Here, we provide evidence that FAN1 is degraded during mitotic exit, suggesting that FAN1 may be a mitotic substrate of the anaphase-promoting cyclosome complex (APC/C). Indeed, Cdh1, but not Cdc20, was capable of regulating the protein level of FAN1 through the KEN box and the D-box. Moreover, the up-and down-regulation of FAN1 affected the progression to mitotic exit. Collectively, these data suggest that FAN1 may be a new mitotic substrate of APC/C Cdh1 that plays a key role during mitotic exit.

SUMOylation stabilizes hSSB1 and enhances the recruitment of NBS1 to DNA damage sites

Human single-stranded DNA-binding protein 1(hSSB1)is required for the efficient recruitment of the MRN complex to DNA doublestrand breaks and is essential for the maintenance of genome integrity.However,the mechanism by which hSSB1 recruits NBS1 remains elusive.Here,we determined that hSSB1 undergoes SUMOylation at both K79 and K94 under normal conditions and that this modification is dramatically enhanced in response to DNA damage.SUMOylation of hSSB1,which is specifically fine-tuned by PIAS2α,and SENP2,not only stabilizes the protein but also enhances the recruitment of NBS1 to DNA damage sites.Cells with defective hSSB1 SUMOylation are sensitive to ionizing radiation,and global inhibition of SUMOylation by either knocking out UBC9 or adding SUMOylation inhibitors significantly enhances the sensitivity of cancer cells to etoposide.Our findings reveal that SUMOylation,as a novel posttranslational modification of hSSB1,is critical for the functions of this protein,indicating that the use of SUMOylation inhibitors(e.g.,2-D08 and ML-792)may be a new strategy that would benefit cancer patients being treated with chemo-or radiotherapy.

The effect of nano-calcium carbonate onβ-glucosidase immobilized by alginate and chitosan

Nanotechnology has become the most promising domain to boost the efficiency of enzymes.Enzymes are vital as a green catalyst in many industries,food,pharmaceutical and biomedical,etc.The immobilization process of the enzyme increases its catalytic properties.In this research,a novel method is presented to describe the effect of nano-calcium carbonate on the characteristics of immobilizedβ-glucosidase,which was extracted from the Agrocybe aegirit.The nano-CaCO_(3)was produced using the eco-friendly natural deep eutectic solvent.The pure nano-CaCO_(3)was observed as vaterite,with a size of about 300 nm.The nano-calcium carbonate was coated by a natural polymer sodium alginate compound and then adsorbed chitosan.Further,this obtained composite is cross-linked by the bioactive genipin to immobilize theβ-glucosidase.The enzyme/protein loading ratio to the supports was 1:4,respectively.The recovery efficiency of immobilizedβ-glucosidase was 89.3%,and immobilization yield was 96.452%.Chitosan-coated nano-CaCO_(3)was used as a carrier for immobilization ofβ-glucosidase to improve its stability and reusability.In addition to stability and reusability,pH tolerance,temperature tolerance,and enzyme kinetics are the significant parameters that illustrate the proficiency of an immobilized enzyme.The measured optimal enzymatic reaction conditions for the immobilizedβ-glucosidase were 50℃and pH 6.Furthermore,it has shown noticeable improvements in thermo-stability and pH tolerance.Temperature tolerance was observed 50%to the initial activity of the immobilized enzyme even after the 3 h of incubation at 50℃,while pH tolerance was noticed more than 50%and 40%at pH 7 and 8,respectively.The K_(m)and V_(max)values of free and immobilizedβ-glucosidase to 4-nitrophenylβ-D-glucopyranoside were 1.549μmol/L/min,0.346 mmol/L and 0.532μmol/L/min,0.080 mmol/L,respectively.The immobilizedβ-glucosidase retains its storability 80%even after 30 days of storage at 4℃and maintains 93.1%of its residual activity by reusing up to 10 cycles.