Cyclin-dependent kinase (CDK)11p110, formerly known as PITSLRE, is a serine/threonine kinase whose catalytic activity has been associated with transcription and RNA processing. To further evaluate the regulation of CDK11p110 catalytic activity, interacting proteins were identified by liquid chromatography and tandem mass spectrometry (LC-MS/MS). Following the immunoprecipitation of CDK11p110 from COS-7 cells, the serine/threonine kinase CK2 was identified by LC-MS/MS. These results were extended through the observation that CDK11p110 serves as a substrate for CK2 and the identification of a phosphorylation site on CDK11 p110 at Ser227 by LC-MS/MS. To obtain CDK11p110 devoid of CK2, CDK11p110 was expressed in High Five insect cells and secreted into the media due to the presence of a honeybee melittin signal sequence encoded at the amino-terminus of CDK11p110. Recombinant CDK11 p110 was purified from the media and phosphorylation of histone H1 subsequently demonstrated. After demonstrating retention of CDK11 p110 kinase activity, it was evaluated for activity on the carboxyl-terminal domain (CTD) of the largest subunit of RNA polymerase II (RNAP II), but only CK2 was found to phosphorylate the CTD.
- CTD, carboxyl-terminal domain of the largest subunit of RNA polymerase II
- High five insect cell
- LC-MS/MS, liquid chromatography and tandem mass spectrometry
ASJC Scopus subject areas
- Molecular Biology