5081
Analysis of Bcl - 2 / Bcl - 2 homodimerization using both in vitro binding assays as well as a yeast two - hybrid method provided evidence in support of a head - to - tail model for Bcl - 2 / Bcl - 2 homodimerization and revealed that sequences within the NH2 - terminal A domain interact with a structure that requires the presence of both the carboxyl B and C domains in combination .
 Bcl - 2, Bcl - 2, Bcl - 2, Bcl - 2
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: GENE 
Text: {0} 
Answer:
 Bcl - 2, Bcl - 2, Bcl - 2, Bcl - 2