A non-covalent interaction between small ubiquitin-like modifier-1 and Zac1 regulates Zac1 cellular functions.
Zac1, a zinc-finger protein that regulates apoptosis and cell cycle arrest 1, such as p53, can induce cell-cycle arrest and apoptosis. The transactivation and coactivation functions of Zac1 may occur at non-promyelocytic leukemia nuclear body (PML-NB) sites in the presence of other PML-NB components, including ubiquitin-conjugating 9 (Ubc9). It is unclear whether post-translational modification of Zac1 by the small ubiquitin-like modifier SUMO plays a role in the coactivation functions of Zac1 for the regulation of the p21 gene. Mutagenesis experiments revealed that the two SUMO-binding lysine residues of Zac1, K237 and K424, repress the transactivation activity of Zac1. Studies using a SUMO-1 C-terminal di-glycine motif mutant that is deficient in the ability to form covalent bonds with lysines, SUMO-1 (GA), and a dominant-negative Ubc9 construct (C93S) indicated that SUMO-1 might regulate Zac1 transactivation and coactivation via a non-covalent interaction. Unlike the wild-type Zac1, which induced apoptosis, the Zac1 (K237/424R) double mutant had the ability to induce autophagy. The functional role of p21 remains to be investigated. SUMO-1 selectively suppressed the induction of the p21 gene and protein by wild-type Zac1 but not by the Zac1 (K237/424R) double mutant. Moreover, wild-type Ubc9 but not Ubc9 (C93S) further potentiated the suppression of SUMO-1 in all Zac1-induced p21 promoter activities. Our data reveal that p21 may be an important factor for the prevention of Zac1-induced apoptosis without affecting autophagosome formation. This work indicates that Zac1 functions are regulated, at least in part, via non-covalent interactions with SUMO-1 for the induction of p21, which is important for the modulation of apoptosis.
Graduate Institute of Medical Sciences, National Defense Medical Center, Taipei 114, Taiwan, ROC.
Shu-Ting
ST
Liu
Yung-Lung
YL
Chang
Wei-Ming
WM
Wang
Min-Huey
MH
Chung
Wei-Shiang
WS
Lin
Wei-Yuan
WY
Chou
Shih-Ming
SM
Huang
D017209:Apoptosis / Q000235:genetics*; D001343:Autophagy; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000235:genetics*; D005786:Gene Expression Regulation; D006367:HeLa Cells; D006801:Humans; D016297:Mutagenesis, Site-Directed; D009154:Mutation / Q000235:genetics; D011485:Protein Binding / Q000235:genetics; D054730:Protein Interaction Domains and Motifs / Q000235:genetics; D011499:Protein Processing, Post-Translational; D025842:SUMO-1 Protein / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D015533:Transcriptional Activation / Q000235:genetics; D025521:Tumor Suppressor Proteins / Q000235:genetics / Q000378:metabolism*; D044763:Ubiquitin-Conjugating Enzymes / Q000235:genetics / Q000378:metabolism; D000098843:Ubiquitin-Conjugating Enzyme UBC9
C493956:CDKN1A protein, human; D018797:Cell Cycle Proteins; D050759:Cyclin-Dependent Kinase Inhibitor p21; C106464:PLAGL1 protein, human; D025842:SUMO-1 Protein; D014157:Transcription Factors; D025521:Tumor Suppressor Proteins; D044763:Ubiquitin-Conjugating Enzymes; D000098843:Ubiquitin-Conjugating Enzyme UBC9