CLP1 acts as the main RNA kinase in mice

• Published in: Biochemical and biophysical research communications Vol. 525; no. 1; pp. 129 - 134
• Main Authors: Fujinami, Hiroyuki, Shiraishi, Hiroshi, Hada, Kazumasa, Inoue, Masanori, Morisaki, Ikuko, Higa, Ryoko, Shin, Toshitaka, Kobayashi, Takashi, Hanada, Reiko, Penninger, Josef M., Mimata, Hiromitsu, Hanada, Toshikatsu
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 23.04.2020
• Subjects: CLP1; NOL9; RNA kinase; siRNA; NOL9; siRNA; RNA kinase; CLP1
• ISSN: 0006-291X; 1090-2104
• DOI: 10.1016/j.bbrc.2020.02.066

CLP1 plays an essential role in the protein complex involved in mRNA 3′-end formation and polyadenylation as well as in the tRNA splicing endonuclease (TSEN) complex involved in the splicing of precursor tRNAs. NOL9 localizes in the nucleolus of cells and plays an essential role in ribosomal RNA maturation. Both CLP1 and NOL9 are RNA kinases that phosphorylate the 5′ end of RNAs. From the evidence that phosphorylation of the 5′ end of a siRNA is essential for its efficient RNA cleavage, it was expected that CLP1 and NOL9 would be corresponding molecules. However, there had been no direct evidence that this is the case. In this study, murine NOL9 showed no apparent RNA kinase activity in cells or even in an RNA kinase assay using recombinant murine NOL9 protein. Although siRNA efficiency was decreased in CLP1 kinase-dead (Clp1K/K) cells, it was not influenced by NOL9 overexpression. These findings indicate that in mouse cells it is CLP1 that mainly acts to phosphorylate the 5′ end of RNAs in the siRNA pathway, with no apparent involvement of NOL9. •RNA kinase activity was not detected in CLP1 kinase-dead mice.•Overexpression of murine NOL9 did not augment RNA kinase activity in cells.•Recombinant murine NOL9 showed no apparent RNA kinase activity.•CLP1, not NOL9, has an important role in the siRNA pathway.