Each method has inherent advantages and limitations, but the combination of these approaches have been successful in identifying many miRNA targets (Table 1). Table 1 List of experimentally validated cellular targets of KSHV- and EBV- encoded miRNAs. The normal cellular functions of these proteins and the effect of their knockdown during viral infection are also listed. The targets that are underlined are repressed by both KSHV- and EBV-encoded miRNAs.
More studies from recent reports indicate miR-K12-5, miR-K12-9 and miR-K12-10 repression of Bcl-2-associated transcription factor 1, an apoptosis-inducing factor (238), miR-K12-3 reduction of LRRC8D (leucine rich repeat containing 8 family, member D), a leucin-rich type III transmembrane protein involved in proliferation and activation of lymphocytes, NHP2L1 (non-histone chromosome protein 2-like 1) (239), and a transcription factor NFIB (240), miR-K12-1 inhibition of p21 241 and NFkappaB inhibitor IkappaBalpha (242), miR-K12-4-3p suppression of GEMIN8 (239), miR-K12-10a reduction of TWEAKR (243), miR-K12-1, -6, and -11 decrease of MAF (musculoaponeurotic fibrosarcoma oncogene homolog) (244), K12-4-5p targeting retinoblastoma (Rb)-like protein 2 (Rbl2) and miR-K12-5 and -9*suppressing ORF50 mRNA (245,246).
Furthermore, miR-K10a-mediated downregulation of TWEAKR prevents TWEAK-induced caspase activation, and alleviating TWEAKR repression in infected cells via a specific miR-K10a inhibitor reverses this effect.
Previous literature suggested TNFRSF12A plays a role in apoptosis and the proinflammatory response. Multiple assays revealed miR-K12-10a repression of TNFRSF12A protects cells from cytokine-induced apoptosis and suppresses a proinflammatory cytokine response induced by TNFSF12/TWEAK.
Our dataset also confirmed 12 out of 29 validated KSHV miRNA targets with expression in our dataset(>40%). Confirmed interactions include those with BACH1, FOS, CDKN1A(p21), TNFRSF12A(TWEAKR), RAD21 and RBL2 mRNAs, whose regulation had previously been validated at the level of protein expression. A list summarizing the recovery of previously published targets of the KSHV and EBV miRNAs is presented in Table S9. NIHMS333942-supplement-01 Table S9 Recovery of previously published targets for KSHV or EBV miRNAs.
Tumor necrosis factor (TNF)-like weak inducer of apoptosis (TWEAK) receptor (TWEAKR) was among the most consistently and robustly downregulated genes in the presence of KSHV miR-K12-10a (miR-K10a).