Our findings highlight the central role of m6A as a negative regulator of type-I IFN response, by dictating the fast turnover of IFN mRNAs and consequently facilitating viral propagation (Winkler et al., Nature Immunology, 2019). In a broader sense, this work demonstrates how studying virus-host interaction can shed light on basic molecular processes of the host cell. These findings suggest a potential parsimonious unifying model for interpreting the plethora of phenotypes associated with depletion of m6A and propagation of a variety of viruses. To date, studies have illustrated the critical role of m6A machinery in diverse development stages, physiology and disease. However, the ultimate challenge is to link specific methylation sites to phenotypes. We deem IFNB to be a perfect candidate to address this challenge as it is a tightly regulated cytokine and subtle destabilization of its mRNA, caused by m6A, can potentially lead to dramatic phenotypes. To address this challenge in an ongoing work we are generating mouse and human cells in which the putative m6A-modified adenosines in IFNB are mutated. We anticipate these cells and mice may provide, for the first time, a direct connection between m6A modification on a specific transcript and a physiological phenotype.
With regard to full characterization of the latency state, one of the obstacles in studying HCMV latency is the heterogeneity in the cell culture models that are being used. We utilized the power of single-cell RNA-seq (scRNA-seq) to unbiasedly examine the viral transcriptome in latency and made the ground-breaking observation that in latency there are mostly quantitative but not qualitative changes in viral gene expression (Shnayder et al. mBio, 2018). This analysis emphasizes undeniable surprising similarity between latent and late lytic transcriptional programs. These results, together with additional analysis we conducted in natural samples, challenge the view of a well-defined HCMV latency-specific transcriptional program that is composed of few selective functional genes. Instead, these measurements raise the possibility of a gradual repression of viral gene expression resulting in low-level expression of a program that resembles late lytic infection stage.
a central withstanding question is- what are the molecular events leading to the viral transcriptional state during latency? We are currently conducting high temporal resolution measurements, at single cell level, of the early steps during latent and infection of different myeloid populations in order to shed light on the molecular events that lead to the wide but repressed viral gene expression in latent cells.
