PP1 regulatory subunit NIPP1 regulates transcription of E2F1 target genes following DNA damage

• Published in: Cancer science 2021-07, Vol.112 (7), p.2739-2752
• Main Authors: Hanaki, Shunsuke, Habara, Makoto, Masaki, Takahiro, Maeda, Keisuke, Sato, Yuki, Nakanishi, Makoto, Shimada, Midori
• Format: Article
• Language: English
• Subjects: Antibodies; Cell cycle; Cell proliferation; CHK1 protein; Chromatin; CRISPR; Cyclin-dependent kinases; Deoxyribonucleic acid; Dephosphorylation; DNA; DNA binding proteins; DNA damage; E2F1; E2F1 protein; Gene expression; Gene silencing; Genes; Genetic aspects; Genetic transcription; Glycerol; Histone H3; histone phosphorylation; Histones; Kinases; Original; Phosphatase; Phosphorylation; Protein kinase A; Protein phosphatase; Proteins; Statistical analysis; transcription; Transcription activation
• ISSN: 1347-9032; 1349-7006
• DOI: 10.1111/cas.14924

DNA damage induces transcriptional repression of E2F1 target genes and a reduction in histone H3‐Thr11 phosphorylation (H3‐pThr11) at E2F1 target gene promoters. Dephosphorylation of H3‐pThr11 is partly mediated by Chk1 kinase and protein phosphatase 1γ (PP1γ) phosphatase. Here, we isolated NIPP1 as a regulator of PP1γ‐mediated H3‐pThr11 by surveying nearly 200 PP1 interactor proteins. We found that NIPP1 inhibits PP1γ‐mediated dephosphorylation of H3‐pThr11 both in vivo and in vitro. By generating NIPP1‐depleted cells, we showed that NIPP1 is required for cell proliferation and the expression of E2F1 target genes. Upon DNA damage, activated protein kinase A (PKA) phosphorylated the NIPP1‐Ser199 residue, adjacent to the PP1 binding motif (RVxF), and triggered the dissociation of NIPP1 from PP1γ, leading to the activation of PP1γ. Furthermore, the inhibition of PKA activity led to the activation of E2F target genes. Statistical analysis confirmed that the expression of NIPP1 was positively correlated with E2F target genes. Taken together, these findings demonstrate that the PP1 regulatory subunit NIPP1 modulates E2F1 target genes by linking PKA and PP1γ during DNA damage. Under normal conditions, Chk1 phosphorylates H3‐pThr11, which induces K9 acetylation, leading to transcriptional activation of E2F1 target genes. PP1 is inactivated through both Cdk‐dependent phosphorylation at pThr311 and binding to NIPP1. In response to DNA damage, ATR‐dependent release of Chk1 from chromatin indirectly suppresses Cdk activity, which results in the activation of PP1 via a reduction in Thr311 phosphorylation, and its release from NIPP1 is mediated by PKA phosphorylation. Activated PP1 dephosphorylates H3‐pThr11 in collaboration with Chk1 released from E2F1, ultimately resulting in the transcriptional repression of genes, such as CDK1 and CCNB1, involved in the cell cycle.