Mode D depicts the importance of nucleic acid regulation of transcription. In this mode, a viral protein mimics the host regulation by either competing for an existing transcription factor (Figure 7, marked D1) , or by modifying the transcription program following a DNA/RNA binding (Figure 7 , marked D2). For example, the Epstein-Barr virus (EBV) encodes an activator protein that is similar to Fos/Jun family (bZIP_1, PF00170. For example, UniProt: Q80GR6, Q8QQX9, Q6USE5, D2Y5S7). The difference in specificity and the dimerization properties of the EBV activator allows the activation of an alternative transcription program [50] .