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We developed retroviral vectors in which the constitutive viral enhancer in the U3 region of the 3' LTR is replaced by an autoregulatory enhancer of the erythroid-specific GATA-1 transcription factor gene .
 3' LTR, erythroid-specific GATA-1 transcription factor gene, U3 region, autoregulatory enhancer, transcription factor, constitutive viral enhancer
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:
 3' LTR, erythroid-specific GATA-1 transcription factor gene, U3 region, autoregulatory enhancer, transcription factor, constitutive viral enhancer