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Substitutions introduced at bases surrounding the ICR2 motif yielded levels of pRNA replication that differed , depending on the maintenance of a putative 5 ' stem - loop structure in the positive strand of the viral genome .
 ICR2 motif
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: GENE 
Text: {0} 
Answer:
 ICR2 motif