[Dynamic phosphorylation of RNA polymerase III holoenzyme subunits from human epidermoid carcinoma cells A431 cultivated under different conditions].
Dynamic phosphorylation in vivo of individual subunits of holoenzyme RNA polymerase III subfractions IIIa and IIIb on serine/threonine and tyrosine aminoacid residues has been shown in human epidermoid carcinoma cells A431. Cells cultivation under starvation on embryonic serum caused a prolongation of the cell cycle, while cultivation at low concentration of epidermal growth factor (EGF) activated cell proliferation. Subunit 45 kDa is phosphorylated on serine/threonine residues in subfraction IIIa only in starving cells. This subunit of subfraction IIIb is unphosphorylated. Phosphorylation of this particular subunit is restored under induction by EGF at low concentration (0.1 ng/ml). The level of phosphorylation on tyrosine aminoacid residues of subunits of holoenzyme subfractions IIIa and IIIb is high in cells cultivated under starvation. Subunit 60 kDa has a higher level of phosphorylation as compared with subunits 45 and 38 kDa. Induction by EGF at low concentrations increases the level of phosphorylation of subunits 60 and 38 kDa in both subfractions of holoenzyme.
Merkulova
N A
NA
Sedova
V M
VM
D002294:Carcinoma, Squamous Cell; D045744:Cell Line, Tumor; D020035:Holoenzymes / Q000378:metabolism; D006801:Humans; D015151:Immunoblotting; D010766:Phosphorylation; D012320:RNA Polymerase III / Q000378:metabolism*
D020035:Holoenzymes; D012320:RNA Polymerase III