The expression of casein kinase 2α′ and phosphatase 2A activity

Protein phosphatase 2A (PP2A) activity may be differentially regulated by the expression of proteins containing a related amino acid sequence motif such as the casein kinase 2 alpha (CK2 alpha) subunit or SV40 small t antigen (SVt). Expression of CK2 alpha increases PP2A activity whereas SVt decreases its activity. In this work we have tested for the effect of the expression of a third protein containing a similar motif that could be involved in PP2A regulation, the catalytic casein kinase 2 alpha' subunit. Our results show that despite the structural similarity of this protein with the other CK2 catalytic (alpha) subunit, the function of the two subunits with respect to the modulation of PP2A activity is quite different: CK2 alpha increases whereas CK2 alpha' slightly decreases PP2A activity. (C) 1999 Elsevier Science B.V. All rights reserved.