Identification and characterization of a JC virus pentanucleotide repeat element binding protein: cellular nucleic acid binding protein

The JC virus (JCV) control region contains AGGGAAGGGA, the tandem pentanucl eotide repeat element (Pnt(2)). Several proteins specifically interacted vi a Pnt(2) to regulate the expression of JCV early promoter-enhancer (JCV(E)) or late promoter-enhancer (JCV(L)). In this study, a JCV Pnt(2) oligonucle otide probe was used to screen a cDNA expression library from glial P19 mou se embryonal carcinoma cells. A cDNA clone was isolated by Southwestern blo t assay and it produced a protein that reproducibly and specifically bound to Pnt(2). This cDNA had 100% homology to one of three previously identifie d mouse cDNAs called cellular nucleic acid binding proteins (Cnbps). Cnbps are a highly homologous family of eukaryotic genes implicated in functional interactions with cytoplasmic RNA and regulatory DNA elements. An mRNA of 2.2 kb of Pnt(2)-interacting Cnbp (PCnbp) was seen in undifferentiated, mus cle or glial P19 cells. When expressed from a cDNA expression vector as a f usion protein that also contained 115 kDa from beta-galactosidase, a Pnt(2) binding protein (PCNBP) specifically bound to Pnt(2) in Southwestern blots as a 30 kDa component of the 145 kDa fusion protein. Furthermore, JCV, exp ression was negatively regulated by PCnbp produced in vivo from the cDNA ex pression vector. Regulation of JCV, was unaffected. We suggest a novel role for CNBP as a PCNBP that interacts with Pnt(2) in the negative transcripti onal regulation of JCV(E). (C) 1998 Elsevier Science B.V. All rights reserv ed.