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Northern analysis of the 3 . 1 - kb PWP2H cDNA revealed that a 3 . 3 - kb major transcript is ubiquitously expressed in human adult tissues .
 3 . 1 - kb PWP2H cDNA
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: GENE 
Text: {0} 
Answer:
 3 . 1 - kb PWP2H cDNA