Characterization and intracellular localization of the Rok1 protein involved in yeast cell division.

ABSTRACT

The ROK1 gene is essential for the cell cycle progression in Saccharomyces cerevisiae. ROK1 has been predicted to encode an ATP-dependent RNA helicase of the DEAD-box family. We have analyzed the ROK1 gene expression both at the protein and RNA levels. Polyclonal antibodies were raised against trpErok1 hybrid proteins and were affinity purified by using lacZrok1 hybrid proteins. Western blot experiments using anti-Rok1 antibodies revealed a single protein band of 64 kDa which is an expected size from the Rok1 amino acid sequence. Indirect immuno-fluorescence showed that the Rok1 protein is localized predominantly to the cytoplasm of the vegetatively growing cells. We have detected immunocross-reactive homologs of Rok1p in Candida albicans and Drosophila melanogaster.