Protein kinase activity associated with the nuclear lamina.
A nuclear lamina-enriched fraction from Ehrlich ascites tumor cells contains a tightly bound protein kinase activity, which phosphorylates in vitro the nuclear lamins, a 52-kilodalton protein, and several unknown minor components. The enzyme(s) is thermolabile, independent of Ca2+ and cAMP, and inhibited by quercetin. After treatment with 4 M urea it remains bound to the nuclear lamina in an active state, but it is irreversibly inactivated in 6 M urea. The lamin proteins are phosphorylated on serine residues. Their two-dimensional phosphopeptide maps show multiple phosphorylation sites and a considerable similarity to the phosphopeptide maps of lamins labeled in vivo. Photoaffinity labeling experiments revealed several polypeptide fractions in the nuclear lamina fraction that are candidates for the protein kinase(s).
Dessev
G
G
Department of Cell Biology and Anatomy, Northwestern University Medical School, Chicago, IL 60611.
Iovcheva
C
C
Tasheva
B
B
Goldman
R
R
D000818:Animals; D002118:Calcium / Q000378:metabolism; D002460:Cell Line; D002467:Cell Nucleus / Q000201:enzymology; D000242:Cyclic AMP / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D007525:Isoelectric Focusing; D034882:Lamins; D008970:Molecular Weight; D009687:Nuclear Proteins / Q000378:metabolism*; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism*; D011794:Quercetin / Q000494:pharmacology
D034882:Lamins; D009687:Nuclear Proteins; D011794:Quercetin; D000242:Cyclic AMP; D011494:Protein Kinases; D002118:Calcium