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In contrast , postmitotic neurons possessed extremely low levels of E2F1 protein as assessed by the electrophoretic mobility shift assay and Western blotting .
 GENE: E2F1 protein
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: GENE 
Text: {0} 
Answer:
 GENE: E2F1 protein