MAGE I Transcription Factors Regulate KAP1 and KRAB Domain Zinc Finger Transcription Factor Mediated Gene Repression
Figure 4
MAGE–KAP1 binding induces ZNF382 ubiquitination in HEK293T cells.
HEK293T cells were transiently transfected with His tagged wild-type MAGE-C2 (WT), mutant (non-binding) MAGE-C2L152A L153A , or empty vectors (Mock) and co-transfected with ZNF382, KAP1, and HA tagged ubiquitin. Cells were incubated for 5 hours in the presence of 25 µM MG132 (C2211, SIGMA). Top two panels: ZNF382 (around 55 kDa), MAGE-C2 (around 50 KD) and KAP1 (110 KD) were detected in whole lysates by immunoblotting with anti-KAP1 (upper panel) and anti-FLAG antibodies (lower panel). Third panel: His tagged ubiquitinated proteins were immunoprecipitated with anti-His and detected with anti-HA. High-molecular-weight ubiquitinated species were seen only in blots of cells transfected with both ZNF382 and MAGE-C2. Note that no ubiquitination occurred when wild type MAGE-C2 was replaced with MAGE-C2L152A L153A which does not bind to KAP1, indicating MAGE–KAP1 binding is required for ZNF382 ubiquitination. Also please note an ubiquitinated ZNF382 degradation product of lesser molecular weight in the presence of wild type MAGE-C2 and KAP1. Lowest panel: immunoprecipitation and immunoblotting confirms expression of ZNF382.