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Evidence for two catalytically active kinase domains in pp90rsk
1Department of Cell Biology, Harvard Medical School, Boston, Massachusetts 02115, USA.
Molecular and Cellular Biology
|March 1, 1996
Summary
The N-terminal domain of ribosomal S6 kinase (RSK) directly phosphorylates key gene regulators, while its C-terminal domain is also active and can be further enhanced by mitogen-activated protein kinase signaling.
Area of Science:
- Molecular Biology
- Cell Signaling
Background:
- Mitogen-activated protein kinase (MAPK) and ribosomal S6 kinase (RSK) are serine/threonine kinases in the Ras signaling pathway.
- RSK possesses two distinct catalytic domains, but their individual activities remain unclear.
Purpose of the Study:
- To determine the catalytic activity of RSK's individual domains.
- To identify the substrates and phosphorylation motifs targeted by RSK domains.
Main Methods:
- In vitro phosphorylation assays.
- Identification of phosphorylated substrates and motifs.
Main Results:
- The N-terminal domain of RSK phosphorylates substrates like serum response factor, c-Fos, Nur77, and ribosomal protein S6.
- These substrates contain an RXXS motif at the phosphorylation site.
- The C-terminal domain of RSK is catalytically active and can be activated by MAPK phosphorylation.
Conclusions:
- RSK's N-terminal domain mediates direct gene expression regulation through specific substrate phosphorylation.
- Both RSK domains are catalytically active, with the C-terminal domain's activity being modulated by MAPK.