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We found that the 3 ' - end - adjacent sequence CA ( N ) 3 - 10AGTNNAA , conserved in plant Pol II - specific U snRNA genes , is essential for the 3 ' - end formation of U2 transcripts and , similar to the vertebrate 3 ' box , is highly tolerant to mutation .
 Pol II, U snRNA genes, U2 transcripts
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: GENE 
Text: {0} 
Answer:
 Pol II, U snRNA genes, U2 transcripts