DBP6P IS AN ESSENTIAL PUTATIVE ATP-DEPENDENT RNA HELICASE REQUIRED FOR SOS-RIBOSOMAL-SUBUNIT ASSEMBLY IN SACCHAROMYCES-CEREVISIAE

A previously uncharacterized Saccharomyces cerevisiae open reading fra me, YNR038W, was analyzed in the context of the European Functional An alysis Network. YNR038W encodes a putative ATP-dependent RNA helicase of the DEAD-box protein family and was therefore named DBP6 (DEAD-box protein 6). Dbp6p is essential for cell viability. In vivo depletion o f Dbp6p results in a deficit in 60S ribosomal subunits and the appeara nce of half-mer polysomes. Pulse-chase labeling of pre-rRNA and steady -state analysis of pre-rRNA and mature rRNA by Northern hybridization and primer extension show that Dbp6p depletion leads to decreased prod uction of the 27S and 7S precursors, resulting In a depletion ok the m ature 25S and 5.8S rRNAs. Furthermore, hemagglutinin epitope-tagged Db p6p is detected exclusively within the nucleolus. We propose that Dbp6 p is required for the proper assembly of preribosomal particles during the biogenesis of 60S ribosomal subunits, probably by acting as an rR NA helicase.