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Single cell assay of a transcription factor reveals a threshold in transcription activated by signals emanating from the T-cell antigen receptor .
 protein: transcription factor; protein: T-cell antigen receptor
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: transcription factor; protein: T-cell antigen receptor