450
From nuclear runoff experiments, we found that one subunit in particular, the B2 isoform (Mr = 56,000), was amplified primarily by transcriptional means .
 B2 isoform
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:
 B2 isoform