MAGE proteins regulate KRAB zinc finger transcription factors and KAP1 E3 ligase activity

Abstract

Expression of Melanoma AntiGen Encoding (MAGE) genes, particularly MAGE-A3, has been correlated with aggressive clinical course, the acquisition of resistance to chemotherapy and poor clinical outcomes of melanoma and other malignancies. MAGE proteins bind to KAP1, a gene repressor and ubiquitin E3 ligase which also binds KRAB domain containing zinc finger transcription factors (KZNFs), and MAGE expression may affect KZNF mediated gene regulation. To investigate mechanisms for these effects, we tested the hypothesis that differences in KRAB domain composition affect KZNF poly-ubiquitination and determine whether MAGE expression increases, decreases, or has no effect on KZNFs mediated gene repression. Using an integrated reporter gene responsive to repression by KRAB domain fusion proteins, we found that MAGE-A3 relieved KZNF mediated repression and induced KZNF poly-ubiquitination and degradation in association with expression of the A+B box KRAB domain. In contrast, MAGE-A3 enhanced KAP1 mediated repression of KZNFs expressing A or A+b box KRAB domains but caused no increase in poly-ubiquitination or degradation. MAGE-A3 has no significant impact on KZNFs with KRAB domains containing the Scan box motif. These data support our hypothesis by showing that the effects of MAGE-A3 on gene repression depend on the type of KZNF KRAB domain involved.

ZNF224, Krüppel like zinc finger protein, induces cell growth and apoptosis-resistance by down-regulation of p21 and p53 via miR-663a

“…However, qRT-PCR of ZNF224 after CPT treatment did not induce any change of ZNF224 mRNA level (data not shown), which suggests a possibility that DNA damage signal may induce degradation of ZNF224 by post-translational modification such as ubiquitination. It is well known that KRAB domain and it's neighboring amino acid sequences are critical to ubiquitination of KRAB-ZFPs [ 42 – 43 ]. Interestingly, KAP1 binds to KRAB domain of KRAB-ZFPs to function as an ubiquitin E3 ligase [ 43 – 44 ].…”

“…It is well known that KRAB domain and it's neighboring amino acid sequences are critical to ubiquitination of KRAB-ZFPs [ 42 – 43 ]. Interestingly, KAP1 binds to KRAB domain of KRAB-ZFPs to function as an ubiquitin E3 ligase [ 43 – 44 ]. In another study, it has been reported that the expression of KAP1 and KRAB-ZFPs was increased in breast carcinoma, and sumoylated-KAP1 protects the KRAB-ZFPs from proteasomal degradation, which promotes proliferation and metastatic progression of breast cancer cells [ 45 ].…”

Cellular and disease functions of the Prader–Willi Syndrome geneMAGEL2

“…For example, MAGEs can stimulate TRIM28 auto-ubiquitination and ubiquitination of substrates, such as p53 and ZNF382, leading to their degradation by the proteasome (18, 33, 34). In addition, MAGE-A1 and MAGE-G1 can stimulate the ligases activity of their cognate E3 RING ligase, TRIM31 and NSE1, respectively (18, 32).…”

Structures of Two Melanoma-Associated Antigens Suggest Allosteric Regulation of Effector Binding

“…Rather, each MAGE protein appears to recognize a unique region on its RING partner, suggesting that MAGE proteins are able to function as a versatile and adaptable protein interaction module. MAGE-A3 was found to interact with the nuclear scaffolding protein and E3 ligase TRIM28 (also known as KAP1), via its RING-B box coiled coil (RBCC) motif [ 15 ], and this interaction was found to stimulate the E3 ligase activity leading to degradation of various targets with roles in apoptosis such as the tumour suppressor p53[ 15 , 17 ], the KRAB zinc finger transcription factor ZNF382[ 18 ], and the metabolic regulator AMP activated protein kinase (AMPK)[ 14 ]. In contrast to MAGE-A3, relatively little is known about the possible interactions of MAGE-A4 with RING containing ligases.…”