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Regulation of E2F involves its interactions with other cellular proteins , including the retinoblastoma protein ( Rb ), the Rb-related protein p107 , cyclin A , and cdk2 .
 cellular proteins, E2F, Rb-related protein, p107, cyclin A, Rb, cdk2, retinoblastoma protein
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: cell line, protein, RNA, DNA, cell type 
Text: {0} 
Answer:
 cellular proteins, E2F, Rb-related protein, p107, cyclin A, Rb, cdk2, retinoblastoma protein