The Leu-enkephalin-encoding sequence DNA-binding factor (LEF) is the transcription factor YY1.

The Leu-enkephalin-encoding sequence DNA-binding factor (LEF) with high affinity for the Leu-enkephalin-encoding sequences in the prodynorphin and proenkephalin genes has earlier been identified. This factor is composed of three subunits of about 60, 70 (the major DNA-binding subunit), and 95 kDa, respectively. Estimated molecular mass, sequence specificity of DNA-binding, and supershift/inhibition with specific antibodies in a band shift assay showed that the DNA-binding subunit of LEF is identical to the multifunctional transcription factor YY1. However, an antibody against the C-terminus of YY1 distinguished the YY1 complexes with a Leu-enkephalin-encoding sequence and canonical YY1 binding site oligonucleotides, suggesting different protein conformations in complexes with these two DNA fragments.