AN EUKARYOTIC RUVB-LIKE PROTEIN (RUVBL1) ESSENTIAL FOR GROWTH

A human protein (RUVBL1), consisting of 456 amino acids (50 kDa) and h ighly homologous to RuvB, was identified by using the 14-kDa subunit o f replication protein A (hsRPA3) as bait in a yeast two-hybrid system. RuvB is a bacterial protein involved in genetic recombination that be ars structural similarity to subunits of the RF-C clamp loader family of proteins. Fluorescence in situ hybridization analysis demonstrated that the RUVBL1 gene is located at 3q21, a region with frequent rearra ngements in different types of leukemia and solid tumors. RUVBL1 co-im munoprecipitated with at least three other unidentified cellular prote ins and was detected in the RNA polymerase II holoenzyme complex purif ied over multiple chromatographic steps. In addition, two yeast homolo gs, scRUVBL1 and scRUVBL2 with 70 and 42% identity to RUVBL1, respecti vely, were revealed by screening the complete Saccharomyces cerevisiae genome sequence. Yeast with a null mutation in scRUVBL1 was nonviable . Thus RUVBL1 is an eukaryotic member of the RuvB/clamp loader family of structurally related proteins from bacteria and eukaryotes that is essential for viability of yeast.