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Updated: Apr 17, 2026

Studying Cell Cycle-regulated Gene Expression by Two Complementary Cell Synchronization Protocols
Published on: June 6, 2017
The mitotic PP2A regulator ENSA/ARPP-19 is remarkably conserved across plants and most eukaryotes
Anne-Marie Labandera1, Ahmad R Vahab1, Sibapriya Chaudhuri1
1Department of Biological Sciences, University of Calgary, Calgary, AB T2N 1N4, Canada.
Abstract:
Protein phosphatase 2A (PP2A) is a major serine/threonine phosphatase of eukaryotes. PP2A containing the B55 subunit is a key regulator of mitosis and must be inhibited by phosphorylated α-endosulfine (ENSA) or cyclic AMP-regulated 19 kDa phosphoprotein (ARPP-19) to allow passage through mitosis. Exit from mitosis then requires dephosphorylation of ENSA/ARPP-19 to relieve inhibition of PP2A/B55. ENSA/ARPP-19 has been characterized in several vertebrates and budding yeast, but little is known about its presence in plants and the majority of other eukaryotes. Here we show that three isoforms of ENSA/ARPP-19 are present in the Arabidopsis thaliana genome with distinct expression profiles across various plant tissues. The ENSA/ARPP-19 proteins, and in particular their key inhibitory sequence FDSGDY (FDSADW in plants), is remarkably conserved across plants and most eukaryotes suggesting an ancient origin and conserved function to control PP2A activity.
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