N-Myristoyltransferase 1 enhances human immunodeficiency virus replication through regulation of viral RNA expression level.

N-myristoyltransferase (NMT) catalyzes protein N-myristoylation. It has been suggested that the isozyme NMT1 enhances the replication of human immunodeficiency virus type-1 (HIV-1). However, the details of the mechanism by which NMT1 does so remain unclear. In this study, we investigated NMT1-binding proteins by co-immunoprecipitation and mass spectrometry. As a result, several RNA-binding proteins including ribosomal proteins, NMT isozymes, and hnRNP A2/B1 were observed to bind to NMT1, as mediated mainly by RNA. Interestingly, only hRNP A2/B1 was found to associate with NMT1 without mediation by RNA. It was also suggested that hnRNP A2/B1 contributes to the formation of complexes of high molecular weights involving NMT1. Knockdown of hnRNP A2/B1 resulted in the enhancement of viral replication with an increase in the expression level of viral RNA in HIV-1-producing cells. On the other hand, knockdown of NMT1 resulted in the attenuation of viral replication with the decrease in the expression level of viral RNA in HIV-1-producing cells. Additionally, overexpression of NMT1 induced the enhancement of viral replication with the increase in the expression level of the viral RNA. These findings suggest that both NMT1 and hnRNP A2/B1 take part in the regulation of HIV-1 RNA expression through their mutual opposite effects on the viral RNA expression in HIV-1-producing cells.