Polyomavirus DNA replication in the pancreas and in a transformed pancreas cell line has distinct enhancer requirements

Abstract

The regulatory DNA (enhancer) of polyomavirus (Py) is a major determinant of tissue-specific DNA replication during acute infection of newborn mice. Previously, we reported that the combination of one of the two Py enhancers (A enhancer) and the repeated Moloney murine leukemia virus (Mo-MuLV) enhancer gave a chimeric Py genome (Py-MuLV) that replicates predominantly in the acinar cells of the pancreas, a tissue not permissive for wild-type PyA2 replication (R. Rochford, B. A. Campbell, and L. P. Villareal, Proc. Nat. Acad. Sci. USA 84: [449][450][451][452][453] 1987). In this report, we further examine the combined enhancer requirements for acinar cell-specific Py replication. We also compare enhancer requirements for Py replication in the acinar cells of the pancreas with those of a transformed acinar cell line (266-6 cells). The deletion of sequences within the A enhancer of Py-MuLV (nucleotides 5098 to 5132) results in a virus with 10-fold-reduced levels of pancreasspecific replication. The deletion, however, of one of the 72-bp repeated Mo-MuLV enhancer sequences from Py-MuLV results in a complete loss of pancreas-specific DNA replication. Thus, the Py A enhancer is required for efficient replication of Py in the pancreas without otherwise altering organ specificity, but both of the repeated copies of the Mo-MuLV enhancer are essential for pancreas-specific Py replication. In contrast to the enhancer requirements for in vivo pancreas replication, in transformed acinar cells (266-6), PyA2 wild-type replicated efficiently and the Py-MuLV recombinant replicated inefficiently. These data suggest that the cellspecific control of DNA replication is different between normal pancreas cells and their transformed cell line counterparts and that this difference is apparent in the enhancer requirement of cell-specific Py DNA replication.

Enhancer dependence of polyomavirus persistence in mouse kidneys

“…We used a mixed-virus infection of mice with three different strains of Py enhancer variants and established that the organs of mice specifically replicate Py DNA and can sort the viral replicon with the compatible enhancer during both the acute and the persistent phases of a viral infection. These results further establish that organspecific DNA replication is a major determinant of cellspecific virus replication, as previously proposed (30,31,33,35). Of specific interest was the ability of PyACR and PyMLV (but not PyA2) to replicate efficiently in the neonatal mouse pancreas.…”

Discrimination between Sialic Acid-Containing Receptors and Pseudoreceptors Regulates Polyomavirus Spread in the Mouse

“…Site-directed mutagenesis is used to introduce substitutions into the VP1s of different wild-type strains, guided by results of X-ray crystallography (32)(33)(34). Differences in noncoding sequences among wild-type strains are common, and these can have significant effects on the extent and tissue specificity of virus replication (1,9,(28)(29)(30) as well as on tumor induction (16,18). By comparing site-directed mutants with parental strains, the effects of VP1 mutations can be assessed in the absence of differential contributions from viral enhancers.…”

Relationship of eukaryotic DNA replication to committed gene expression: general theory for gene control.

“…If transformed cells do indeed have aberrant (mixed) replication control, their ability to amplify DNA and divide is not unexpected. We have examined the difference in cell type control of polyomavirus DNA replication in normal pancreas cells compared with transformed pancreatic cell lines (310) and observed that transformed pancreatic cell lines supported the full replication of wildtype polyomavirus, but we saw no replication in the pancreas in vivo, even though other polyomavirus enhancer variants can replicate in the pancreas (307). The transformed (mitotic) line thus displayed a relaxed control over cellspecific viral DNA amplification, even though these cells were expressing many pancreas-specific genes (276,277).…”