It is now emerging that many proteins are regulated by a variety of covalent modifications. Using microcystin-affinity chromatography we have purified multiple protein phosphatases and their associated proteins from Arabidopsis thaliana. One major protein purified was the histone deacetylase HDA14. We demonstrate that HDA14 can deacetylate α-tubulin, associates with α/β-tubulin and is retained on GTP/taxol-stabilized microtubules, at least in part, by direct association with the PP2A-A2 subunit. Like HDA14, the putative histone acetyltransferase ELP3 was purified on microcystin-Sepharose and is also enriched at microtubules, potentially functioning in opposition to HDA14 as the α-tubulin acetylating enzyme. Consistent with the likelihood of it having many substrates throughout the cell, we demonstrate that HDA14, ELP3 and the PP2A A-subunits A1, A2 and A3 all reside in both the nucleus and cytosol of the cell. The association of a histone deacetylase with PP2A suggests a direct link between protein phosphorylation and acetylation.
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