Cooperative action of cellular proteins YB-1 and Pur alpha with the tumor antigen of the human JC polyomavirus determines their interaction with the viral lytic control element.

Abstract

Human JC polyomavirus (JCV) is the etiologic agent of the neurodegenerative disease progressive multifocal leukoencephalopathy. By using JCV as a model, we investigated the role of the viral early protein tumor antigen (TAg) in the binding of two cellular proteins, Pura and YB-1, to JCV regulatory sequences. Results from band-shift assays with purified YB-1, Purca, and TAg indicated that efficient binding of Pura, a strong activator ofearly gene transcription, to a single-stranded target sequence corresponding to the viral lytic control element, is diminished in the presence of the late gene activator YB-1, which recognizes the opposite strand of the Pura binding site. Of particular interest was the ability of Pura and TAg to enhance binding ofYB-1 to DNA molecules without being associated with this complex. Binding studies using a mutant peptide encompassing the N terminus ofYB-1 indicated that the C terminus ofYB-1 is important for its DNA binding activity. The ability of Purax and TAg to increase binding ofYB-1 to DNA is independent ofthe YB-1 C terminus. Similarly, results from band-shift assays using Pura variants indicated that two distinct regions of this protein contribute either to its ability to bind DNA or to its ability to enhance YB-1 DNA binding activity. Based on the interaction of Pura, YB-1, and TAg, and their binding to DNA, a model is proposed for the role of these proteins in transcription ofviral early and late genes during the lytic cycle.to cell-specific transcriptional factors, other regulatory proteins found in various cells and tissues are believed to be critical in facilitating viral gene expression during the lytic cycle (13-18). Results from this (10-12, 17, 19) and other (9,20) laboratories have indicated that the 98-bp enhancer/promoter sequence of JCV encompasses multiple cis-regulatory elements that interact specifically with nuclear proteins and modulate viral early and late gene transcription. A region designated the lytic control element (LCE) in the 98-bp repeat proximal to the origin of DNA replication contains a pentanucleotide repeat sequence, AGGGAAGGGA, juxtaposed to a poly(dT-dA) tract that displays a single-stranded configuration (21). This motif differentially affects viral gene expression by positively and negatively modulating early and late promoter transcription (17,19) and plays an important role in viral DNA replication (22,23). In this study we demonstrate that two distinct cellular proteins, Pura and YB-1, activators for the early and late gene transcription of JCV, respectively, modulate each other's binding to the LCE. Moreover, we show that the viral early protein TAg is capable of enhancing binding of YB-1 to DNA molecules. We propose a working model for the potential role of LCE-binding proteins and the viral TAg in programming the early-to-late shift of the viral gene transcription during the lytic cycle.

Androgen Receptor Overexpression in Prostate Cancer Linked to Purα Loss from a Novel Repressor Complex

“…Both Pura (38)(39)(40) and hnRNP-K (34, 41) can strand-separate dsDNA and subsequently bind to the individual DNA strands. Nuclear extracts of AD and AI cells retarded the single C-and G-rich ssARS probes ( Fig.…”

During Differentiation of the Monocytic Cell Line U937, Purα Mediates Induction of theCD11cβ2 Integrin Gene Promoter

“…In addition to homotypic interaction, Pur␣ has been shown to interact with a range of different cellular proteins (11,(22)(23)(24)(25)(26). Such interactions may account for the complex nature of the supershift obtained upon analysis of the Pur␣ complex that interacts with the Ϫ41/Ϫ29 region (Fig.…”

“…The functional activity of Pur␣ has been shown to be influenced either in a positive or negative manner by its interaction with a number of cellular proteins, including calmodulin, Sp1, YB-1, Pur␤, and the retinoblastoma protein Rb (11,(22)(23)(24)(25)(26). Of these proteins, only Sp1 has been reported to influence CD11c gene expression (4, 19 -21, 27).…”

Involvement of a single‐stranded DNA binding protein, ssCRE‐BP/Purα, in morphine dependence

“…Thus, the effect of casein on the DNA binding activity of ssCRE-BP/Purc~ seemed to be specific. Recent reports showed that ssCRE-BP/Pur~ interacts with viral transcription regulatory tumor antigen (TAg) of human JC polyomavirus (JCV) which induces demyelinated plaques within the brain of patients, and with the late gene transcription activator of JCV, YB-1, which inhibits the DNA binding activity of ssCRE-BP/Purc~ to the pur element [24]. ssCRE-BP/Pur~ can be associated with a variety of proteins and acquire different functions in the transcription and replication in different cells.…”