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The p38-interacting protein (p38IP) regulates G2/M progression by promoting ?-tubulin acetylation via inhibiting ubiquitination-induced degradation of the acetyltransferase GCN5.

ABSTRACT: p38-interacting protein (p38IP) is a component of the GCN5 histone acetyltransferase-containing coactivator complex (GCN5-SAGA complex). It remains unclear whether p38IP or GCN5-SAGA is involved in cell cycle regulation. Using RNA interference to knock down p38IP, we observed that cells were arrested at the G2/M phase, exhibiting accumulation of cyclins, shrunken spindles, and hypoacetylation of ?-tubulin. Further analysis revealed that knockdown of p38IP led to proteasome-dependent degradation of GCN5. GCN5 associated with and acetylated ?-tubulin, and recovering GCN5 protein levels in p38IP knockdown cells by ectopic expression of GCN5 efficiently reversed ?-tubulin hypoacetylation and G2/M arrest. During the G2/M transition, the association of ?-tubulin with GCN5 increased, and the acetylation of ?-tubulin reached a peak. Biochemical analyses demonstrated that the interaction between p38IP and GCN5 depended on the p38IP N terminus (1-381 amino acids) and GCN5 histone acetyltransferase domain and bromodomain. The p38IP N terminus could effectively reverse p38IP depletion-induced GCN5 degradation, thus recovering ?-tubulin acetylation and G2/M progression. p38IP-mediated suppression of GCN5 ubiquitination most likely occurs via nuclear sequestration of GCN5. Our data indicate that the GCN5-SAGA complex is required for G2/M progression, mainly because p38IP promotes the acetylation of ?-tubulin by preventing the degradation of GCN5, in turn facilitating the formation of the mitotic spindle.

SUBMITTER: Liu X

PROVIDER: S-EPMC3868776 | biostudies-literature | 2013 Dec

REPOSITORIES: biostudies-literature

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The p38-interacting protein (p38IP) regulates G2/M progression by promoting α-tubulin acetylation via inhibiting ubiquitination-induced degradation of the acetyltransferase GCN5.

Liu Xin X Xiao Wei W Wang Xu-Dong XD Li Yue-Fang YF Han Jiahuai J Li Yingqiu Y

The Journal of biological chemistry 20131112 51

p38-interacting protein (p38IP) is a component of the GCN5 histone acetyltransferase-containing coactivator complex (GCN5-SAGA complex). It remains unclear whether p38IP or GCN5-SAGA is involved in cell cycle regulation. Using RNA interference to knock down p38IP, we observed that cells were arrested at the G2/M phase, exhibiting accumulation of cyclins, shrunken spindles, and hypoacetylation of α-tubulin. Further analysis revealed that knockdown of p38IP led to proteasome-dependent degradation ...[more]

PMID: 24220028

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Project description:The histone acetylation of post-translational modification can be highly dynamic and play a crucial role in regulating cellular proliferation, survival, differentiation and motility. Of the enzymes that mediate post-translation modifications, the GCN5 of the histone acetyltransferase (HAT) proteins family that add acetyl groups to target lysine residues within histones, has been most extensively studied. According to the mechanism studies of GCN5 related proteins, two key processes, deprotonation and acetylation, must be involved. However, as a fundamental issue, the structure of hGCN5/AcCoA/pH3 remains elusive. Although biological experiments have proved that GCN5 mediates the acetylation process through the sequential mechanism pathway, a dynamic view of the catalytic process and the molecular basis for hGCN5/AcCoA/pH3 are still not available and none of theoretical studies has been reported to other related enzymes in HAT family. To explore the molecular basis for the catalytic mechanism, computational approaches including molecular modeling, molecular dynamic (MD) simulation and quantum mechanics/molecular mechanics (QM/MM) simulation were carried out. The initial hGCN5/AcCoA/pH3 complex structure was modeled and a reasonable snapshot was extracted from the trajectory of a 20 ns MD simulation, with considering post-MD analysis and reported experimental results. Those residues playing crucial roles in binding affinity and acetylation reaction were comprehensively investigated. It demonstrated Glu80 acted as the general base for deprotonation of Lys171 from H3. Furthermore, the two-dimensional QM/MM potential energy surface was employed to study the sequential pathway acetylation mechanism. Energy barriers of addition-elimination reaction in acetylation obtained from QM/MM calculation indicated the point of the intermediate ternary complex. Our study may provide insights into the detailed mechanism for acetylation reaction of GCN5, and has important implications for the discovery of regulators against GCN5 enzymes and related HAT family enzymes.

Dataset Information

The p38-interacting protein (p38IP) regulates G2/M progression by promoting ?-tubulin acetylation via inhibiting ubiquitination-induced degradation of the acetyltransferase GCN5.

Publications

The p38-interacting protein (p38IP) regulates G2/M progression by promoting α-tubulin acetylation via inhibiting ubiquitination-induced degradation of the acetyltransferase GCN5.

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