FOSB and Kaposi's sarcoma: Other viruses including feline immunodeficiency virus [55], foamy viruses [56], [57], Kaposi's sarcoma associated herpes virus [58], [59], human papillomavirus [60], [61], visna virus [62] or human T-cell leukemia/lymphoma virus type I (HTLV-I) [63], [64] use AP-1 factors either to regulate their own replication or to interfere with host cell gene regulation.