p34cdc2 phosphorylation sites in histone H1 are dephosphorylated by protein phosphatase 2A1

Protein phosphatase 2A subunit assembly: the catalytic subunit carboxy terminus is important for binding cellular B subunit but not polyomavirus middle tumor antigen

“…Thus, the loss of B subunit binding (Figure 2a) correlates with a dramatic decrease in phosphatase activity against cdc2 phosphorylated histone H1. This result con®rms previous ®ndings of others regarding B subunit modulation of PP2A speci®city (Sola et al, 1991;Agostinis et al, 1992;Ferrigno et al, 1993;Mayer-Jaekel et al, 1994), but, in addition, indicates that mutation of the C subunit can indirectly generate the same phenotype.…”

“…For example, the B subunit greatly increases PP2A activity towards cdc2 phosphorylated histone H1 (Sola et al, 1991;Agostinis et al, 1992;Ferrigno et al, 1993;Mayer-Jaekel et al, 1994). PP2A regulation during the development in di erent tissues may therefore occur in part through di erential expression of the various subunits (for review, see Mumby and Walter, 1993).…”

Dephosphorylation of distinct sites on microtubule‐associated protein MAP1B by protein phosphatases 1, 2A and 2B

“…Similar results have been obtained upon studying the PPZA-catalyzed dephosphorylation of microtubule-associated tau protein at the tau-1 epitope [30], which is a site phosphorylated by proline-directed protein kinases including cdc2 kinase [31,32]. In addition, histone HI phosphorylated by the cdc3 kinase was also best dephosphorylated by PP2A [33]. It is not known whether an increase in phosphatase activity and/or a decrease in kinase activity is/are responsible for the net dephosphorylation on MAPlB at the 150 epitope which is observed during axonal maturation [9,17].…”

Protein phosphatase 2A is associated in an inactive state with microtubules through 2A1-specific interaction with tubulin

“…major peaks of the activity ( Figure 1A). The second peak activity was found at 0n37 M NaCl ( Figure 1A), 50 % inhibited by okadaic acid at 0n5 nM (not shown) and thus judged to be PP2A2 from the NaCl concentration required for the elution from the Mono-Q and the sensitivity to the inhibition by okadaic acid [18,38,39]. The first peak found at 0n31 M NaCl, was judged to be PP2A1 from the NaCl concentration for the elution and the sensitivity to okadaic acid [18,38,39].…”

“…The second peak activity was found at 0n37 M NaCl ( Figure 1A), 50 % inhibited by okadaic acid at 0n5 nM (not shown) and thus judged to be PP2A2 from the NaCl concentration required for the elution from the Mono-Q and the sensitivity to the inhibition by okadaic acid [18,38,39]. The first peak found at 0n31 M NaCl, was judged to be PP2A1 from the NaCl concentration for the elution and the sensitivity to okadaic acid [18,38,39]. PP1 or PP2A0 reported to elute at 0n25 M NaCl or less [38,40] was hardly detected possibly because of loss of the unstable enzymes and\or omission of the activation procedures used for these enzymes [40].…”