Functions as a DNA-binding transcription factor. Promotes transformation, host cell growth, host cell-cycle progression through G1/S phase, and possesses antiapoptotic activity. Forms functional heterodimers with host JUN. These heterodimers bind with high affinity DNA sequences called MEQ-responsive elements MERE I (TGACA/GTCA), while MEQ homodimers bind a second type of sites termed MERE II (ACACA). Both homo and heterodimerization of MEQ are required for oncogenesis. Homodimer. Interacts with host JUN; this interaction allows MEQ to engage in host cell processes by disguising itself as a cellular JUN. Expressed in both the nucleus and the cytoplasm during the G1/S boundary and early S phase of host cell cycle. Phosphorylated by host CDK2; this phosphorylation greatly reduces the DNA binding activity of MEQ. Belongs to the bZIP family. Jun subfamily.