Biology subjects

Djakovic, L.

Publications and source records attributed to Djakovic, L..

5 recordsLinked to original sources

bioRxiv2024

HSV-1 infection induces a downstream-shift of +1 nucleosomes

Herpes simplex virus 1 (HSV-1) infection induces a loss of host transcriptional activity and widespread disruption of host transcription termination, which leads to an induction of open chromatin downstream of genes. In this study, we show that lytic HSV-1 infection also leads to an extension of chromatin accessibility at promoters into downstream regions. This is most prominent for highly expressed genes and independent of the immediate-early proteins ICP0, ICP22, and ICP27 and the virion host shutoff protein vhs. ChIPmentation of the noncanonical histone variant H2A.Z, which is strongly enriched at +1 and -1 nucleosomes, indicated that these chromatin accessibility changes are linked to a downstream shift of +1 nucleosomes. In yeast, downstream shifts of +1 nucleosomes are induced by RNA Polymerase II (Pol II) degradation. Accordingly, irreversible depletion of Pol II from genes in human cells using -amanitin altered +1 nucleosome positioning similar to lytic HSV-1 infection. Consequently, treatment with phosphonoacetic acid (PAA) and knockout of ICP4, which both prevent viral DNA replication and alleviate the loss of Pol II from host genes, largely abolished the downstream extension of accessible chromatin in HSV-1 infection. In the absence of viral DNA replication, doxycycline-induced expression of ICP27, which redirects Pol II from gene bodies into intergenic regions by disrupting transcription termination, induced an attenuated effect that was further enhanced by co-expression of ICP22. In summary, our study provides strong evidence that HSV-1-induced depletion of Pol II from the host genome leads to a downstream shift of +1 nucleosomes at host promoters. ImportanceLytic herpes simplex virus 1 (HSV-1) infection leads to a profound host transcription shutoff. Loss of RNA Polymerase II (Pol II) in yeast has previously been shown to relax +1 nucleosome positioning to more thermodynamically favorable sites downstream of transcription start sites. Here, we show that a similar phenomenon is likely at play in lytic HSV-1 infection. Sequencing of accessible chromatin revealed a widening of nucleosome-free regions at host promoters into downstream regions. By mapping genome-wide positions of the noncanonical histone variant H2A.Z enriched at +1 and -1 nucleosomes, we demonstrate a downstream shift of +1 nucleosomes for most cellular genes in lytic HSV-1 infection. As chemical depletion of Pol II from genes also leads to a downstream shift of +1 nucleosomes in human cells, changes in chromatin architecture at promoters in HSV-1 infection are likely a consequence of HSV-1-induced loss of Pol II activity from the host genome.

bioinformatics↗

bioRxiv2022

HSV-1 infection induces a downstream shift of promoter-proximal pausing linked to H2A.Z-containing +1 nucleosomes

Herpes simplex virus 1 (HSV-1) infection exerts a profound shut-off of host gene expression at multiple levels. Recently, HSV-1 infection was reported to also impact promoter-proximal RNA Polymerase II (Pol II) pausing, a key step in the eukaryotic transcription cycle, with decreased and increased Pol II pausing observed for activated and repressed genes, respectively. Here, we demonstrate that HSV-1 infection induces more complex alterations in promoter-proximal pausing than previously suspected for the vast majority of cellular genes. While pausing is generally retained, it is shifted to more downstream and less well-positioned sites for most host genes. We exclude that this is an artefact of alternative de novo transcription initiation at downstream sites or read-in transcription originating from disruption of transcription termination for upstream genes. Use of downstream 2nd pause sites associated with +1 nucleosomes was previously observed upon NELF depletion. However, downstream shifts of Pol II pausing upon HSV-1 infection are much more pronounced than observed upon NELF depletion. Thus, our study reveals a novel aspect in which HSV-1 infection fundamentally reshapes host transcriptional processes with implications for our understanding of maintenance of promoter-proximal Pol II pausing in eukaryotic cells.

molecular biology↗

bioRxiv2021

HSV-1 and influenza infection induce linear and circular splicing of the long NEAT1 isoform

The herpes simplex virus 1 (HSV-1) virion host shut-off (vhs) protein cleaves both cellular and viral mRNAs by a translation-initiation-dependent mechanism. Here, we show that vhs-mediated degradation of mRNAs leads to an accumulation of circular RNAs (circRNAs) relative to linear mRNAs during HSV-1 infection. Strikingly, we found that circular splicing of the long isoform (NEAT1_2) of the nuclear paraspeckle assembly transcript 1 (NEAT1) was massively induced during HSV-1 infection. In contrast to other circRNAs, induction of the NEAT1_2 circRNA was independent of vhs and occurred while NEAT1_2 was still bound to the chromatin. This was associated with induction of linear splicing of NEAT1_2 both within and downstream of the circRNA. NEAT1_2 splicing was absent in uninfected cells but can be induced by ectopic co-expression of the HSV-1 immediate-early proteins ICP22 and ICP27. Interestingly, NEAT1_2 circular and linear splicing was also up-regulated in influenza A virus (IAV) infection but absent in stress conditions, which disrupt transcription termination similar to but not by the same mechanisms as HSV-1 and IAV infection. Large-scale analysis of published RNA-seq data uncovered induction of NEAT1_2 splicing in cancer cells upon inhibition or knockdown of cyclin-dependent kinase 7 (CDK7) or the MED1 subunit of the Mediator complex phosphorylated by CDK7. Finally, CDK7 inhibition also disrupted transcription termination, highlighting a possible link between disruption of transcription termination and NEAT1_2 splicing.

bioinformatics↗

bioRxiv2020

Mechanism and consequences of herpes simplex virus 1-mediated regulation of host mRNA alternative polyadenylation

Eukaryotic gene expression is extensively regulated by cellular stress and pathogen infections. We have previously shown that herpes simplex virus 1 (HSV-1) and several cellular stresses cause widespread disruption of transcription termination (DoTT) of RNA polymerase II (RNAPII) in host genes and that the viral immediate early factor ICP27 plays an important role in HSV-1-induced DoTT. Here, we show that HSV-1 infection also leads to widespread changes in alternative polyadenylation (APA) of host mRNAs. In the majority of cases, polyadenylation shifts to upstream poly(A) sites (PAS), including many intronic PAS. Mechanistically, ICP27 contributes to HSV-1-mediated APA regulation. HSV-1- and ICP27-induced activation of intronic PAS is sequence-dependent and does not involve general inhibition of U1 snRNP. HSV1-induced intronic polyadenylation is accompanied by early termination of RNAPII. Finally, HSV-1-induced mRNAs polyadenylated at intronic PAS are exported into the cytoplasm while APA isoforms with extended 3 UTRs are sequestered in the nuclei, both preventing the expression of the full-length gene products. Together with other recent studies, our results suggest that viral infection and cellular stresses induce a multi-faceted host shutoff response that includes DoTT and changes in APA profiles.

molecular biology↗

bioRxiv2020

Dissecting HSV-1-induced host shut-off at RNA level

Herpes simplex virus 1 (HSV-1) installs a profound host shut-off during lytic infection. The virion host shut-off (vhs) protein plays a key role in this process by efficiently cleaving both host and viral mRNAs in a translation-initiation-dependent manner. Furthermore, the onset of viral DNA replication is accompanied by a rapid decline in transcriptional activity of the host genome. Both mechanisms have tremendous impact on the RNA expression profile of the infected cells. To dissect their relative contributions and elucidate gene-specific host transcriptional responses throughout the first 8h of lytic HSV-1 infection, we here employed RNA-seq of total, newly transcribed (4sU-labelled) and chromatin-associated RNA in wild-type (WT) and {Delta}vhs infection of primary human fibroblasts. Following virus entry, vhs activity rapidly plateaued at an elimination rate of around 30% of cellular mRNAs per hour until 8h p.i. In parallel, host transcriptional activity dropped down to 10-20%. While the combined effects of both phenomena dominated infection-induced changes in total RNA, extensive gene-specific transcriptional regulation was observable in chromatin-associated RNA. This was surprisingly concordant between WT HSV-1 and its {Delta}vhs mutant and at least in parts mediated by the embryonic transcription factor DUX4. Furthermore, both WT and {Delta}vhs infection induced strong transcriptional up-regulation of a small subset of genes. Most of these were either poorly or not at all expressed prior to infection but already primed by H3K4me3 histone marks at their promoters. Most interestingly, analysis of chromatin-associated RNA revealed vhs-nuclease-activity-dependent transcriptional down-regulation of at least 150 cellular genes, in particular of many genes encoding integrin adhesome and extracellular matrix components. This was accompanied by a vhs-dependent reduction in protein levels by 8h p.i. for many of these genes. In summary, our study provides a comprehensive picture of the molecular mechanisms that govern cellular RNA metabolism during the first 8h of lytic HSV-1 infection. Author SummaryThe HSV-1 virion host shut-off (vhs) protein efficiently cleaves both host and viral mRNAs in a translation-dependent manner. In this study, we model and quantify changes in vhs activity as well as the virus-induced global loss of host transcriptional activity during productive HSV-1 infection. In general, HSV-1-induced alterations in total RNA levels were found to be predominantly shaped by these two global processes rather than gene-specific regulation. In contrast, chromatin-associated RNA depicted gene-specific transcriptional changes. This revealed highly concordant transcriptional changes in WT and{Delta} vhs infection, confirmed DUX4 as a key transcriptional regulator in HSV-1 infection and depicted vhs-dependent, transcriptional down-regulation of the integrin adhesome and extracellular matrix. The latter explained some of the gene-specific effects previously attributed to vhs-mediated mRNA degradation and resulted in a concordant loss in protein levels by 8h p.i. for many of the respective genes.

microbiology↗