6227
Most importantly , the addition of purified 17S U2 snRNPs , but not of 12S U2 snRNPs , to HeLa splicing extracts in which the endogeneous U2 snRNPs have been functionally neutralized with anti - PRP9 antibodies fully restores the mRNA - splicing activity of the extracts .
 17S U2 snRNPs, 12S U2 snRNPs, endogeneous U2 snRNPs, anti - PRP9 antibodies
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: GENE 
Text: {0} 
Answer:
 17S U2 snRNPs, 12S U2 snRNPs, endogeneous U2 snRNPs, anti - PRP9 antibodies