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We have determined that several E1 mutants mapping in both the M and R regions and a single mutant of the upstream regulatory region have a higher transforming activity on mouse C127 cells than the wild - type genome does .
 E1 mutants
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: GENE 
Text: {0} 
Answer:
 E1 mutants