The Functional Characterization Of Proteins KIAA1751 And XLF

To ensure genome integrity and prevent aneuploidy,eukaryotes have evolved an integrated protective mechanism,including cell cycle control,checkpoint control,and DNA repair.When a cell senses DNA damage,replication stress,or abnormal mitosis, it recruits and activates a series of signal transducers and effectors,thus halting from entering into the next ophase of the cell cycle.DNA double-strand break(DSB) is probably the most lethal attack,with as little as one unrepaired DSB being capable of triggering programmed cell death.Homologous recombination(HR) and nonhomologous end-joining(NHEJ) are the major cellular DSB repair pathways.This thesis research contains two parts:(1) KIAA1751 is an ASH domain-containing protein.This domain is present in proteins associated with cilia,flagella,the centrosome,and the Golgi complex,and possesses a microtubule-binding function.This research has showed that KIAA1751 mainly locates in the nucleus,mutation of its ASH domain does not affect its localization.We have also found that depletion of KIAA1751 by siRNA leads to a defective spindle checkpoint activation induced by taxol,indicating that KIAA1751 is involved in the spindle checkpoint control.(2) By interacting with the XRCC4-DNA ligase IV complex,the NHEJ core factor XLF stabilizes and stimulates the DNA ligase to the damaged DNA.The human RecQ family helicase WRN,which is mutated in the Werner syndrome, possesses both helicase and 3'-5' exonuclease activities.Before the ligation of XRCC4-DNA ligase IV complex and damaged DNA terminal,WRN interacts with this complex by binding to XRCC4.Here we have confirmed that depletion of XLF leads cellular defects in DNA repair,and have found that XLF itself along with WRN positively regulates the transcription of XLF.