Identification of a short amino acid sequence essential for efficient nuclear targeting of the Kaposi's sarcoma-associated herpesvirus/human herpesvirus-8 K8 protein.

The K8 protein of Kaposi's sarcoma-associated herpesvirus (KSHV)/human herpesvirus-8 is a member of the bZIP family of transcription factors, which has homology with the Epstein-Barr virus transcription and replication factor, EB1. In this report, we have analysed the subcellular localization of the K8 protein and characterized a 12 amino acid sequence rich in basic residues which is responsible for targeting the protein to the cell nucleus. Furthermore, we show that a K8 mutant lacking the nuclear localization sequence can be directed to the nucleus by co-expression with an intact K8 protein, suggesting that K8 homodimerizes in the cytoplasm of the cell in vivo.