Interaction of a paraneoplastic cerebellar degeneration-associated neuronal protein with the nuclear helix-loop-helix leucine zipper protein MRG X.

Paraneoplastic cerebellar degeneration-associated antigen PCD17/cdr2 is a neuronal protein expressed predominantly in the cytoplasm of cerebellar Purkinje cells. The biological activities of this protein are not known; however, the presence of a leucine zipper motif in its amino acid sequence suggests that this protein might interact with other proteins harboring a leucine zipper motif. In this study we found by means of a yeast two-hybrid system, ligand overlay assay, and co-immunoprecipitation assay that PCD17 interacts with a nuclear helix-loop-helix leucine zipper protein, MRG X. Overexpression of MRG X in T98G glioblastoma cells by transfection caused abnormal morphological changes in the nucleus and induced cell death. On the other hand, coexpression of PCD17 with MRG X prevented nuclear morphological changes and cell death in T98G cells. MRG X, which is thought to be functionally related to the cell cycle and cell growth, may be regulated by PCD17/cdr2 in Purkinje cells. (c) 2002 Elsevier Science (USA).