Molecular interplay between T-Antigen and splicing factor, arginine/serine-rich 1 (SRSF1) controls JC virus gene expression in glial cells

Abstract

BackgroundHuman polyomavirus JCV is the etiologic agent of progressive multifocal leukoencephalopathy (PML), a fatal demyelinating disease characterized by lytic infection of glial cells in the central nervous system. PML is seen primarily in immunosuppressed patients and is mainly classified as an AIDS-defining disease. In addition to structural capsid proteins, JCV encodes multiple regulatory proteins, including T-antigen and agnoprotein, which are required for functional lytic infection. Previous studies have suggested that molecular interaction between viral proteins and host factors play an important role in reactivation of JCV and progression of the viral life cycle in glial cells. Recently, serine/arginine rich splicing factor 1 (SRSF1), a cellular alternative splicing factor, was identified as a strong negative regulator of JCV in glial cells. SRSF1 inhibits JCV gene expression and viral replication by directly interacting with viral promoter sequences. Here, we have investigated possible impact of JCV regulatory proteins, T-antigen and agnoprotein, on SRSF1-mediated suppression of JCV gene expression in glial cells.ResultsReporter gene analysis has suggested that T-antigen rescues viral transcriptional suppression mediated by SRSF1. Further analyses have revealed that T-antigen promotes viral gene expression by suppressing SRSF1 gene transcription in glial cells. A subsequent ChIP analysis revealed that T-antigen associates with the promoter region of SRSF1 to induce the transcriptional suppression.ConclusionsThese findings have revealed a molecular interplay between cellular SRSF1 and viral T-antigen in controlling JCV gene expression, and may suggest a novel mechanism of JCV reactivation in patients who are at risk of developing PML.

Pur-Alpha Induces JCV Gene Expression and Viral Replication by Suppressing SRSF1 in Glial Cells

“…The ability of Pur-alpha to induce JCV reactivation has been well established by our group during the last two decades [ 29 – 31 ]. More recently, we have identified another cellular gene, SRSF1, which functions as a suppressor of JCV reactivation [ 19 – 21 , 32 ]. Even though they function inversely in regulation of JCV gene expression, Pur-alpha and SRSF1 share several similarities including regulation of mRNA as well as serving as transcription factors.…”

“…The efficiency and productivity of viral replication depends on a delicate balance among host factors which are positive and negative regulators of viral gene expression and DNA replication. SRSF1 is an important host gene controlling JC virus gene expression in glial cells [ 19 – 21 , 32 ]. We have recently showed that SRSF1 expression is regulated by immune signaling, and can be induced by soluble immune mediators (cytokines and chemokines) leading to transcriptional suppression of JC virus [ 33 ].…”

“…Two important cellular proteins which are capable of regulating JCV gene expression and viral replication include Pur-alpha and SRSF1. We recently identified the alternative splicing factor, SRSF1, as a potential regulator of JCV whose overexpression in glial cells strongly suppresses viral gene expression and replication [ 19 – 21 ]. Down-regulation of JCV by SRSF1 is mediated at the step of splicing of the JCV early genes including T-antigen pre-mRNA as well as at the step of viral early gene transcription thus ascribing an important role for SRSF1 in the control of JCV gene expression.…”

“…In the nucleus, it associates with cellular DNA to activate or suppress transcription of a number of cellular genes including myelin basic protein, gata2, TNFα, TGFβ, and E2F1 as well as the Pur-alpha promoter itself [ 24 ] and interacts with a number of key cellular regulatory proteins including Rb, E2F1, and several cyclins and cdks [ 22 , 25 , 26 ]. In the cytoplasm, Pur-alpha plays an increasingly recognized role as a critical component in mRNA translation [ 21 , 27 , 28 ]. Pur-alpha is a potent inducer of JCV replication through direct induction of viral gene expression and binding to the key viral regulatory protein, T-antigen [ 22 , 29 – 31 ].…”

Alcohol-Mediated Missplicing of Mcl-1 Pre-mRNA is Involved in Neurotoxicity

“…The luciferase reporter plasmid pLuc-SRSF1 was made by cloning the −1000 to +49 promoter region of SRSF1 gene into the pGL3 vector at the BamH1 site and was described previously (Craigie et al, 2015; Sariyer et al, 2016). Human serine and arginine rich splicing factor 1 (SRSF1, NCBI Reference Sequence: NM_006924.4) was cloned into the eukaryotic expression vector pcDNA ™ 6/myc-His at Hind-III and Xho-I restriction enzyme sites and labeled as pcDNA ™ 6/myc-His-SRSF1.…”