| MAT 1 is an assembly / targeting factor for cyclin dependent kinase activating kinase ( CAK ) , which has been shown to functionally interact with general transcriptional factor TFIIH , a known inducer of ER transactivation . ^^^ In addition , MAT 1 interacts with the activation function 2 domain of ER and colocalizes with ER in activated cells . ^^^ Together , these findings identified MAT 1 as a target of MTA 1 and provided new evidence to suggest that the transactivation functions of ER might be influenced by the regulatory interactions between CAK and MTA 1 in breast cancer cells . . ^^^ MTA 1 interacts with MAT 1 , a cyclin dependent kinase activating kinase complex ring finger factor , and regulates estrogen receptor transactivation functions . ^^^ |