Conservation of virally encoded MicroRNAs in kaposi sarcoma-associated herpesvirus in primary effusion lymphoma cell lines and in patients with kaposi sarcoma or multicentric Castleman disease

Background. MicroRNAs are small noncoding RNAs that posttranscriptionally regulate gene expression. Kaposi sarcoma ( KS)-associated herpesvirus ( KSHV) encodes 12 distinct microRNA genes, all of which are located within the latency-associated region that is highly expressed in all KSHV-associated malignancies. Methods. We amplified, cloned, and sequenced a 2.8-kbp-long region containing a cluster of 10 microRNAs plus a 646-bp fragment of K12/T0.7 containing the remaining 2 microRNAs from 5 primary effusion lymphoma derived cell lines and from 17 patient samples. The patients included 2 with classic KS, 12 with AIDS-KS ( 8 from the United States, 1 from Europe, 3 from Africa, and 4 from Central/South America), and 2 with multicentric Castleman disease ( MCD). Additionally, we analyzed the K1, open reading frame 75, and K15 genes to determine KSHV subtypes, and we performed a phylogenetic analysis. Results. Phylogenetic analysis of the 2.8-kbp microRNA region revealed 2 distinct clusters of sequences: a major ( A/C) and a variant ( B/Q) cluster. The variant cluster included sequences from 3 patients of African origin and both patients with MCD. Some microRNAs were highly conserved, whereas others had changes that could affect processing and, therefore, biological activity. Conclusions. These data demonstrate that KSHV microRNA genes are under tight selection in vivo and suggest that they contribute to the biological activity and possibly the pathogenesis of KSHV-associated malignancies.