1981
A consensus binding site for the transcription factor SP1 was identified in intron As downstream of the proenkephalin germ cell cap site region .
 SP1, proenkephalin germ cell cap site region
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: GENE 
Text: {0} 
Answer:
 SP1, proenkephalin germ cell cap site region