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CLP1 acts as the main RNA kinase in mice

Hiroyuki Fujinami1, Hiroshi Shiraishi2, Kazumasa Hada2

  • 1Department of Cell Biology, Oita University Faculty of Medicine, Yufu, Oita, 879-5593, Japan; Department of Urology, Oita University Faculty of Medicine, Yufu, Oita, 879-5593, Japan.

Biochemical and Biophysical Research Communications
|February 22, 2020
PubMed

Insights

In mouse cells, CLP1, not NOL9, phosphorylates the 5' end of small interfering RNAs (siRNAs) for efficient RNA cleavage. This clarifies the roles of these RNA kinases in the siRNA pathway.

Area of Science:

  • Molecular Biology
  • RNA Biology
  • Biochemistry

Background:

  • CLP1 and NOL9 are known RNA kinases involved in RNA processing.
  • CLP1 functions in mRNA 3'-end formation and tRNA splicing.
  • NOL9 is essential for ribosomal RNA maturation and localizes to the nucleolus.

Purpose of the Study:

  • To investigate the roles of CLP1 and NOL9 in the RNA interference (RNAi) pathway.
  • To determine if NOL9 possesses RNA kinase activity and contributes to siRNA processing.
  • To clarify the specific RNA kinase responsible for 5' end phosphorylation of siRNAs in mouse cells.

Main Methods:

  • Assessing RNA kinase activity of recombinant murine NOL9 protein in vitro.
  • Evaluating siRNA efficiency in CLP1 kinase-dead (Clp1K/K) cells.
  • Measuring the impact of NOL9 overexpression on siRNA efficiency.

Main Results:

  • Murine NOL9 exhibited no detectable RNA kinase activity in vitro or in cellular assays.
  • siRNA efficiency was reduced in Clp1K/K cells, indicating CLP1's role.
  • Overexpression of NOL9 did not affect siRNA efficiency.

Conclusions:

  • CLP1 is the primary RNA kinase responsible for phosphorylating the 5' end of siRNAs in mouse cells.
  • NOL9 does not appear to be involved in the siRNA pathway's RNA phosphorylation step.
  • These findings delineate the specific functions of CLP1 and NOL9 in RNA metabolism and RNAi.
Keywords:
CLP1NOL9RNA kinasesiRNA

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