Transcription factor that binds to and transactivates the vitellogenin II (VTG2) promoter. Binds to the palindromic sequence 5'-GTTTACATAAAC-3'. Binds DNA as a homodimer or a heterodimer. Exists as a stable dimer in the absence of DNA. Isoform 1 and isoform 3 are expressed in a variety of somatic tissues, including liver, heart, intestine, stomach and kidney. Both isoforms are also expressed in hepatoma (LMH) cells and in embryonic fibroblast cell lines. Isoform 2 and isoform 4 are expressed in adult heart and intestine. Isoform 3 is expressed as early as embryonic day 10. Produced by alternative promoter usage. Produced by alternative promoter usage. Produced by alternative splicing of isoform 1. Produced by alternative splicing of isoform 2. Belongs to the bZIP family. PAR subfamily.