Silencing of RNA helicase II/Gualpha inhibits mammalian ribosomal RNA production.
The intricate production of ribosomal RNA is well defined in yeast, but its complexity in higher organisms is barely understood. We recently showed that down-regulation of nucleolar protein RNA helicase II/Gualpha (RH-II/Gualpha or DDX21) in Xenopus oocytes inhibited processing of 20 S rRNA to 18 S and contributed to degradation of 28 S rRNA (Yang, H., Zhou, J., Ochs, R. L., Henning, D., Jin, R., and Valdez, B. C. (2003) J. Biol. Chem. 278, 38847-38859). Since no nucleolar RNA helicase has been functionally characterized in mammalian cells, we used short interfering RNA to search for functions for RH-II/Gualpha and its paralogue RH-II/Gubeta in rRNA production. Silencing of RH-II/Gualpha by more than 80% in HeLa cells resulted in an almost 80% inhibition of 18 and 28 S rRNA production. This inhibition could be reversed by exogenous expression of wild type RH-II/Gualpha. A helicase-deficient mutant form having ATPase activity was able to rescue the production of 28 S but not 18 S rRNA. A phenotype exhibiting inhibition of 18 S and 28 S rRNA production was also observed when the paralogue RH-II/Gubeta was overexpressed. Both down-regulation of RH-II/Gualpha and overexpression of RH-II/Gubeta slowed cell proliferation. The opposite effects of the two paralogues suggest antagonistic functions.
Henning
Dale
D
Department of Pharmacology, Baylor College of Medicine, Houston, Texas 77030, USA.
So
Rolando B
RB
Jin
Runyan
R
Lau
Lester F
LF
Valdez
Benigno C
BC
D000251:Adenosine Triphosphatases / Q000378:metabolism; D000818:Animals; D015153:Blotting, Western; D002455:Cell Division; D002460:Cell Line; D002466:Cell Nucleolus / Q000378:metabolism; D053487:DEAD-box RNA Helicases; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation; D005434:Flow Cytometry; D020868:Gene Silencing; D005822:Genetic Vectors; D006367:HeLa Cells; D006801:Humans; D007700:Kinetics; D051379:Mice; D009154:Mutation; D009865:Oocytes / Q000378:metabolism; D010641:Phenotype; D012313:RNA / Q000378:metabolism*; D020365:RNA Helicases / Q000235:genetics* / Q000502:physiology*; D012335:RNA, Ribosomal / Q000378:metabolism; D034741:RNA, Small Interfering / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012270:Ribosomes / Q000378:metabolism*; D013997:Time Factors; D014162:Transfection; D014981:Xenopus
D012335:RNA, Ribosomal; D034741:RNA, Small Interfering; D012313:RNA; D000251:Adenosine Triphosphatases; C501726:DDX21 protein, human; C410330:DDX56 protein, human; D053487:DEAD-box RNA Helicases; D020365:RNA Helicases