Helios belongs to the Ikaros transcription factor family. Members of this family are DNA binding proteins containing two-zinc finger N terminal domains and protein binding domain. Helios expression is restricted to the T lymphocytes lineage. Helios is suggested to play an important role in CD4+CD25+FoxP3+ regulatory cells. It has been shown that Helios up-regulates the expression of FoxP3 expression by binding to the FoxP3 promoter. Helios is a highly conserved transcription factor that has 97% sequence homology between human and mice.

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