Serine 62-Phosphorylated MYC Associates with Nuclear Lamins and Its Regulation by CIP2A Is Essential for Regenerative Proliferation

An understanding of the mechanisms determining MYC’s transcriptional and proliferation-promoting activities in vivo could facilitate approaches for MYC targeting. However, post-translational mechanisms that control MYC function in vivo are poorly understood. Here, we demonstrate that MYC phosphorylation at serine 62 enhances MYC accumulation on Lamin A/C-associated nuclear structures and that the protein phosphatase 2A (PP2A) inhibitor protein CIP2A is required for this process. CIP2A is also critical for serum-induced MYC phosphorylation and for MYC-elicited proliferation induction in vitro. Complementary transgenic approaches and an intestinal regeneration model further demonstrated the in vivo importance of CIP2A and serine 62 phosphorylation for MYC activity upon DNA damage. However, targeting of CIP2A did not influence the normal function of intestinal crypt cells. These data underline the importance of nuclear organization in the regulation of MYC phosphorylation, leading to an in vivo demonstration of a strategy for inhibiting MYC activity without detrimental physiological effects. [Display omitted] •Serine 62-phosphorylated MYC is regulated by CIP2A in Lamin A/C-associated complexes•CIP2A is required for MYC S62 phosphorylation during proliferation induction in vivo•MYC activity can be systemically targeted without detrimental physiological effects•We identify a phosphorylation switch defining the DNA damage response in vertebrates Myant et al. demonstrate a specific essential phosphorylation event for in vivo activity of the oncoprotein MYC. This phosphorylation and MYC-mediated proliferation in vivo requires the PP2A phosphatase inhibitor protein CIP2A. Therefore, CIP2A targeting may allow the inhibition of MYC activity for therapies in hyperproliferative diseases.