<；P>；PROBLEM TO BE SOLVED: To find out a gene encoding a protein having the possibility of participating in development and aggravation of tumor diseases and to provide a means for regulating actions of the protein and a means useful for preventing and treating diseases caused by an abnormality of the protein. <；P>；SOLUTION: A DNA in which the expression is accelerated in a tumor tissue is found out and the protein encoded with the DNA is found to exhibit the dephosphorylating activity, bind to CSE1L (chromosome segregation gene 1-like) and dephosphorylate the CSE1L and participate in the cell proliferation. On the basis thereof, a method for inhibiting cell proliferation and an inhibitor characterized as inhibiting the expression and/or function of the protein are provided. A method for inhibiting dephosphorylation of the CSE1L and a dephosphorylation inhibitor thereof, a method for preventing and treating the tumor diseases and a preventing and treating agents are provided. A method for identifying a compound inhibiting the cell proliferation, a compound inhibiting the binding of the protein to the CSE1L and a compound inhibiting the dephosphorylation of the CSE1L with the protein, a method for judging the tumor tissue by measuring the expression level of the DNA in the tissue and a reagent kit are provided. <；P>；COPYRIGHT: (C)2008,JPO&INPIT
