14631
Potential phosphorylation sites include the sequence PSPTSPT , which resembles an RNA polymerase II repeat reported to be a target of the cell cycle control kinase cdc2 .
 RNA polymerase II repeat, cell cycle control kinase cdc2, PSPTSPT, phosphorylation sites
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:
 RNA polymerase II repeat, cell cycle control kinase cdc2, PSPTSPT, phosphorylation sites