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The proto-oncogene products c-Fos and c-Jun heterodimerize through their leucine zippers to form the AP-1 transcription factor .
 protein: proto-oncogene products; protein: leucine zippers; protein: c-Fos; protein: AP-1 transcription factor; protein: c-Jun
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: cell line, protein, RNA, DNA, cell type 
Text: {0} 
Answer:
 protein: proto-oncogene products; protein: leucine zippers; protein: c-Fos; protein: AP-1 transcription factor; protein: c-Jun