The latency protein LANA2 from Kaposi's sarcoma-associated herpesvirus inhibits apoptosis induced by dsRNA-activated protein kinase but not RNase L activation.

Kaposi's sarcoma-associated herpesvirus (KSHV) uses several strategies to counteract the interferon (IFN) system. In this study, the relationship of the protein LANA2 from KSHV to the IFN-activated protein kinase (PKR) and 2-5A system was analysed. It was found that LANA2 could not abrogate apoptosis or RNA degradation mediated by the 2-5A system. However, expression of LANA2 inhibited apoptosis triggered by PKR. LANA2 also counteracted the PKR-mediated inhibition of protein synthesis and partially blocked PKR-induced phosphorylation of eIF-2alpha. Analysis of PKR-induced activation of caspases 3 and 9 revealed that LANA2 abrogated activation of caspase 3 but not of caspase 9. These findings show that LANA2 is able to interfere with downstream events triggered by PKR. Hence, LANA2 should be considered as a KSHV defence protein against IFN.