| In this report , a novel target of MK 2 has been identified , the ETS transcription factor family member ER 81 , whose dysregulation contributes to tumorigenesis and whose normal function is required during development . ^^^ MK 2 phosphorylates ER 81 in vitro within its central inhibitory domain , and overexpression of MK 2 leads to increased in vivo phosphorylation of ER 81 . ^^^ Two serine residues , ER 81 amino acids 191 and 216 , were identified as MK 2 phosphorylation sites . ^^^ MK 2 suppresses basal ER 81 dependent transcription , and this suppressive effect is alleviated upon mutation of the MK 2 phosphorylation sites in a cell type specific manner . ^^^ However , MK 2 can also interfere with ER 81 mediated transcription independently of serine 191 and serine 216 phosphorylation . ^^^ |