ASSOCIATION OF NUCLEOSIDE DIPHOSPHATE KINASE NM23-H2 WITH HUMAN TELOMERES

Telomeres, the ends of eukaryotic chromosomes, are essential structure s formed by specific protein-RNA complexes that protect chromosomes fr om degradetion and end-to-end fusion. TRF1, a double-stranded telomeri c TTAGGG-repeat binding protein, is associated with mammalian telomere s and controls telomere length by inhibiting the action of telomerase. We identified human nucleoside diphosphate kinase nm23-H2 as a human TRF1-interacting protein by yeast two-hybrid screening. In vitro-bindi ng assays using different recombinant nucleoside diphosphate kinases s howed that TRF1 predominantly binds the nm23-H2 isoform rather than nm 23-H1. Electrophoretic mobility shift analysis revealed that the recom binant nm23-H2 protein can bind the single-stranded telomeric TTAGGG-r epeat while it cannot bind the double-stranded telomeric repeat. The s ynthetic 20 base oligoribonucleotide, which consists of the template s equence CUAACCCUAAC and the adjacent region of the RNA component of hu man telomerase, was also found to form the complex with the recombinan t nm23-H2 protein. Furthermore, the affinity of telomerase for its sub strate was increased in vitro by presence of the plentiful nm23-H2 pro tein. These findings indicate a close relationship between nm23-H2 and human telomeres and suggest a new biological role for nucleoside diph osphate kinase. (C) 1998 Academic Press.