Biosynthesis of casein kinase II in lymphoid cell lines

Abstract

We have analyzed the biosynthesis of casein kinase II. In exponentially growing tissue culture cells, the β subunit was synthesized in excess of the catalytic subunit (α). A substantial fraction of newly synthesized β was degraded within the first hour. The remaining fraction of β was incorporated into holoenzyme. In contrast, little degradation of newly synthesized α subunit was observed and most was quickly and efficiently incorporated into holoenzyme. The assembly of β with α was paralleled by an increase in apparent molecular mass of β due to phosphorylation. The subcellular distribution of newly synthesized [35S]Met‐labelled casein kinase II and of enzyme labelled and chased in the presence of excess unlabelled methionine was very similar and compatible with a nuclear localization. The degradation of the excess β subunit occurred through a non‐lysosomal proteolytic system with a very low ATP requirement. Copyright © 1994, Wiley Blackwell. All rights reserved