THE PROTEIN FAMILY OF RNA HELICASES

RNA helicases represent a large family of proteins that have been dete cted in almost all biological systems where RNA plays a central role. They are ubiquitously distributed over a wide range of organisms and a re involved in nuclear and mitochondrial splicing processes, RNA editi ng, rRNA processing, translation initiation, nuclear mRNA export, and mRNA degradation. RNA helicases are described as essential factors in cell development and differentiation, and some of them play a role in transcription and replication of viral single-stranded RNA genomes. Co mparisons of the conserved sequences reveal a close relationship betwe en them and suggest that these proteins might be derived from a common ancestor. Biochemical studies have revealed a strong dependence of th e unwinding activity on ATP hydrolysis. Although RNA helicase activity has only been demonstrated for a few examples yet, it is generally be lieved that all members of the largest subgroups, the DEAD and DEAH bo x proteins, exhibit this activity.