HIV-1 Infection Reduces NAD Capping of Host Cell snRNA and snoRNA

Abstract

Nicotinamide adenine dinucleotide (NAD) is a critical component of the cellular metabolism and also serves as an alternative 5′ cap on various RNAs. However, the function of the NAD RNA cap is still under investigation. We studied NAD capping of RNAs in HIV-1-infected cells because HIV-1 is responsible for the depletion of the NAD/NADH cellular pool and causing intracellular pellagra. By applying the NAD captureSeq protocol to HIV-1-infected and uninfected cells, we revealed that four snRNAs (e.g., U1) and four snoRNAs lost their NAD cap when infected with HIV-1. Here, we provide evidence that the presence of the NAD cap decreases the stability of the U1/HIV-1 pre-mRNA duplex. Additionally, we demonstrate that reducing the quantity of NAD-capped RNA by overexpressing the NAD RNA decapping enzyme DXO results in an increase in HIV-1 infectivity. This suggests that NAD capping is unfavorable for HIV-1 and plays a role in its infectivity.

If the 5’ cap fits (wear it) – Non-canonical RNA capping

“…Apart from DXO, an alternative decapping pathway to DXO in human cell lines involves the cluster of differentiation 38 (CD38) [ 99 ]. These glycoproteins are present on the surface of a number of immune cells and have versatile roles in cellular signalling and adhesion, often using NAD as a substrate [ 100 ]. CD38 glycoproteins convert the NAD cap into an adenosine diphosphate ribose (ADPr) moiety that itself represents another type of non-canonical RNA cap [ 101 ].…”