Transcriptional regulation of human JC polyomavirus promoters by cellular proteins YB-1 and Pur alpha in glial cells

Abstract

Transcription of the human polyomavirus (JCV) genome is regulated by host cell proteins and the viral early protein, T antigen. A region called the lytic control element (LCE), located within the enhancer of JCV, is important for transcription of JCV early and late promoters. Earlier studies have led to the identification of two single-stranded DNA-binding proteins, YB-1 and Pur alpha, with the ability to interact with nucleotides on the early and late strands of LCE, respectively. Of particular interest is the notion that the unique interplay between these two cellular proteins and JCVT antigen determines their binding activities with the LCE. In this study, we employed a series of cotransfection experiments to evaluate the levels of transcription from JCV early and late promoters in the presence of YB-1, Pur alpha, and T antigen. Results from these studies indicated that Pur alpha stimulates JCV early and has little effect on the late promoter. Moreover, T antigen was able to decrease the induced level of early gene transcription by Pur alpha. On the other hand, the extent of transactivation of the viral late promoter by T antigen was reduced upon overexpression of Pur alpha in the transfected cells. These observations suggest that Pur alpha and T antigen exert an antagonistic effect on each other's regulatory action upon their responsive promoters. Of particular interest was the observation that YB-1 liberated T-antigen-induced late promoter activity from repression imposed by overexpression of pur alpha. Under similar conditions, overexpression of YB-1 showed no effect on the transcriptional activity of the early promoter in cells transfected with T-antigen- and Pur alpha-producing plasmids. On the basis of the data presented here and the previous binding results, a model is proposed which describes the potential role of Pur alpha, YB-1, and T antigen in differential expression of the viral genome during the lytic cycle.

JCPyV NCCR analysis in PML patients with different risk factors: exploring common rearrangements as essential changes for neuropathogenesis

“…As have been previously described by other authors, the TATA box and the first half of the C-block appear to be indispensable for viral replication. This portion of the C-block contains NF-1 binding site that is a cellspecific regulator in JCPyV early transcription and replication [13]. In the C-block, immediately adjacent to the NF-1 site, there is the AP-1 binding site, a stimulatory factor involved in JCPyV early gene expression in the absence of viral regulatory proteins [14].…”

“…JCPyV genome is characterized by the presence of early and late genes, which encode for non-structural and structural proteins, respectively, and are separated by the non-coding control region (NCCR), which is a key regulatory region of about 400 bp, harboring the origin of viral DNA replication ori, TATA-, TATA-like sequences, several transcription factor binding sites, promoter/enhancer elements and the binding sites for the viral large T-antigen [12]. Among the transcription factor binding sites harbored in the NCCR, the nuclear transcription factor-1 (NF-1) is a cell-specific regulator of JCPyV promoter/enhancer activity [13]; the activating protein 1 (AP-1) is a stimulatory factor involved in JCPyV early gene expression in the absence of viral regulatory proteins [14]; the specificity protein-1 (SP-1) regulates the JCPyV transcription [15]. One of the most remarkable features of the JCPyV is the rearrangement of the promoter/enhancer elements of the NCCR.…”

RNA‐mediated neurodegeneration in repeat expansion disorders

“…In DM1, some of these changes may still be explained by sequestration of MBNL1, although it remains unclear if this reflects a direct role of MBNL1 in transcriptional regulation or an indirect effect through altered splicing of critical transcription factors 44. In FXTAS, some of these effects may be mediated by Pur α, which can act as a transcriptional repressor 46, 47…”

Early growth response-1 protein is induced by JC virus infection and binds and regulates the JC virus promoter

“…Primary cultures of human fetal astrocytes were prepared and grown as we have previously reported (Radhakrishnan et al, 2003). Reporter constructs, JCV E -CAT and JCV L -CAT contained the JCV promoter from the Mad-1 strain linked to the chloramphenicol acetyltransferase (CAT) gene in the early and late orientations respectively (Chen and Khalili, 1995). pCMV-Sp1 expresses Sp1 from the CMV promoter (Sawaya et al, 1998) and pCMV-Egr-1 expresses Egr-1 from the CMV promoter (Papanikolaou and Sabban, 2000).…”