The p38-interacting protein (p38IP) regulates G2/M progression by promoting α-tubulin acetylation via inhibiting ubiquitination-induced degradation of the acetyltransferase GCN5.
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 of GCN5. GCN5 associated with and acetylated α-tubulin, and recovering GCN5 protein levels in p38IP knockdown cells by ectopic expression of GCN5 efficiently reversed α-tubulin hypoacetylation and G2/M arrest. During the G2/M transition, the association of α-tubulin with GCN5 increased, and the acetylation of α-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 α-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 α-tubulin by preventing the degradation of GCN5, in turn facilitating the formation of the mitotic spindle.
From the Key Laboratory of Gene Engineering of the Ministry of Education, State Key Laboratory of Biocontrol, School of Life Sciences, Sun Yat-sen University, Guangzhou 510275 and.
Xin
X
Liu
Wei
W
Xiao
Xu-Dong
XD
Wang
Yue-Fang
YF
Li
Jiahuai
J
Han
Yingqiu
Y
Li
D000107:Acetylation; D020134:Catalytic Domain; D016213:Cyclins / Q000378:metabolism; D059565:G2 Phase Cell Cycle Checkpoints; D006367:HeLa Cells; D006801:Humans; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D059748:Proteolysis; D008941:Spindle Apparatus / Q000378:metabolism; D014157:Transcription Factors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D014404:Tubulin / Q000378:metabolism*; D054875:Ubiquitination; D050880:p300-CBP Transcription Factors / Q000378:metabolism*; D000099224:p300-CBP-Associated Factor
D016213:Cyclins; D046988:Proteasome Endopeptidase Complex; D014157:Transcription Factors; D014404:Tubulin; D050880:p300-CBP Transcription Factors; D000099224:p300-CBP-Associated Factor; C502592:SUPT20H protein, human
Acetylation; Cell Biology; Cell Cycle; Cell Signaling; Gene Silencing; Molecular Cell Biology; Protein Degradation; gcn5; p38IP; α-Tubulin