LNA is the most immunodominant major latent nuclear antigen discovered when we developed KSHV serologic assays. LNA encoded by ORF73 has since been shown to be a multi-functional viral protein that maintains the stability of viral episomes and regulates viral and cellular gene transcriptions. We have recently identified an array of LNA-interacting proteins by yeast-two hybrid screen. One of such protein, named LNA-interacting protein 1 (KLIP1), is a novel nuclear protein. Primary characterization has demonstrated that KLIP1 is a potent transcriptional repressor and its expression is cell cycle dependent. Several other identified LNA-interacting proteins are also involved in the regulation of cellular gene transcription. We are currently characterizing the biologic function of KLIP1 and the significance of the interactions of LNA with these cellular proteins.
We have generated LNA stably-transfected HeLa cell lines and examined the global regulation of cellular gene expression by LNA using microarray. A total of 45 cellular genes had significant changes in expression levels, and some of them have been confirmed by Northern-blot analysis and real-time RT-PCR. Besides genes that are involved in cell cycle progression and apoptosis, LNA also regulates the expression of genes that are involved in other signaling pathways. Studies are ongoing to examine the upstream and downstream regulation of these genes.
We have also identified a hypervariable internal repeat domain (IRD) of LNA. Based on the variability of IRD, we have developed a novel genotyping technique, named KVNAtyping, that can be used for the characterization of LNA molecular polymorphism and molecular epidemiologic studies of KSHV (see below). We are determining the correlation of IRD variations with LNA functions.