The object of the present invention is to provide a novel protein having a kinase activity and a gene encoding said protein. According to the present invention, there is provided a GANP protein which is represented by the amino acid sequence shown in SEQ ID No. 1 or No. 3 of the sequence listing, and is involved in the signal conversion of abnormal B cell differentiation in an autoimmune state, and has a kinase activity, and a polynucleotide which encodes said protein.