passages.id: split_6_test_858_passage
passages.type: progene_text
passages.text: An S27N mutant of M-Ras , like the analogous H-Ras S17N mutant , was a dominant inhibitor of activation of the c-fos promoter by constitutively active Src Y527F , suggesting that M-Ras and p21 Ras shared guanine nucleotide exchange factors and are likely to be activated in parallel .