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

Laboratoire de virologie humaine, U412 INSERM, ENS-Lyon, 46 allée d’Italie, 69364 Lyon cedex 07, France 1 Author for correspondence: Henri Gruffat. Fax +33 4 72 72 87 77. e-mail hgruffat{at}cri.ens-lyon.fr 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 .