Role of Kaposi's Sarcoma-Associated Herpesvirus C-Terminal LANA Chromosome Binding in Episome Persistence

Abstract

ABSTRACT Kaposi's sarcoma-associated herpesvirus (KSHV) LANA is an 1,162-amino-acid protein that tethers terminal repeat (TR) DNA to mitotic chromosomes to mediate episome persistence in dividing cells. C-terminal LANA self-associates to bind TR DNA. LANA contains independent N- and C-terminal chromosome binding regions. N-terminal LANA binds histones H2A/H2B to attach to chromosomes, and this binding is essential for episome persistence. We now investigate the role of C-terminal chromosome binding in LANA function. Alanine substitutions for LANA residues 1068 LKK 1070 and 1125 SHP 1127 severely impaired chromosome binding but did not reduce the other C-terminal LANA functions of self-association or DNA binding. The 1068 LKK 1070 and 1125 SHP 1127 substitutions did not reduce LANA's inhibition of RB1-induced growth arrest, transactivation of the CDK2 promoter, or C-terminal LANA's inhibition of p53 activation of the BAX promoter. When N-terminal LANA was wild type, the 1068 LKK 1070 and 1125 SHP 1127 substitutions also did not reduce LANA chromosome association or episome persistence. However, when N-terminal LANA binding to chromosomes was modestly diminished, the substitutions in 1068 LKK 1070 and 1125 SHP 1127 dramatically reduced both LANA chromosome association and episome persistence. These data suggest a model in which N- and C-terminal LANA cooperatively associates with chromosomes to mediate full-length LANA chromosome binding and viral persistence.