Stepwise RNP assembly at the site of H/ACA RNA transcription in human cells.
Mammalian H/ACA RNPs are essential for ribosome biogenesis, premessenger RNA splicing, and telomere maintenance. These RNPs consist of four core proteins and one RNA, but it is not known how they assemble. By interrogating the site of H/ACA RNA transcription, we dissected their biogenesis in single cells and delineated the role of the non-core protein NAF1 in the process. NAF1 and all of the core proteins except GAR1 are recruited to the site of transcription. NAF1 binds one of the core proteins, NAP57, and shuttles between nucleus and cytoplasm. Both proteins are essential for stable H/ACA RNA accumulation. NAF1 and GAR1 bind NAP57 competitively, suggesting a sequential interaction. Our analyses indicate that NAF1 binds NAP57 and escorts it to the nascent H/ACA RNA and that GAR1 then replaces NAF1 to yield mature H/ACA RNPs in Cajal bodies and nucleoli.
Darzacq
Xavier
X
Department of Anatomy and Structural Biology, Albert Einstein College of Medicine Bronx, NY 10461, USA.
Kittur
Nupur
N
Roy
Sujayita
S
Shav-Tal
Yaron
Y
Singer
Robert H
RH
Meier
U Thomas
UT
D001667:Binding, Competitive; D002460:Cell Line; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000502:physiology*; D006367:HeLa Cells; D006801:Humans; D008954:Models, Biological; D009687:Nuclear Proteins / Q000378:metabolism; D012313:RNA / Q000378:metabolism*; D020718:Ribonucleoproteins, Small Nucleolar / Q000096:biosynthesis* / Q000378:metabolism; D014158:Transcription, Genetic
D004268:DNA-Binding Proteins; C485802:GAR1 protein, human; C107170:NAP57; D009687:Nuclear Proteins; D020718:Ribonucleoproteins, Small Nucleolar; C117046:TNIP1 protein, human; D012313:RNA