Common features of polyomavirus mutants selected on PCC4 embryonal carcinoma cells.

Abstract

The genomic rearrangements of six polyomavirus mutants selected on PCC4 embryonal carcinoma cells have been compared and their common characteristics pointed out. All mutants show a duplication which includes at least the adenovirus type 5 (Ad5) ElA-like enhancer core sequence plus a deletion of variable size and location. The presence of the second enhancer core sequence, the SV40-like enhancer, is not required for expression of the PyEC PCC4 phenotype. Two of these mutants are also able to express polyomavirus T antigen on F9 and LT1 cells. Multiadaptation seems to require the duplication of the Ad5 ElA-like core sequence, the maintenance of the SV40-like core sequence and a local change in DNA stability.

Multiple sequence motifs are involved in SV40 enhancer function.

“…polyoma virus variants (reviewed in Ruley and Fried, 1983;Melin et al, 1985). The chimeric enhancer (pA411 and pA401) appears to be 50-60% as efficient as the wild-type pAO SV40 enhancer, which is particularly striking, since the isolated polyoma virus enhancer domain A (pA400, pA410) is as inefficient in stimulating transcription as the isolated SV40 domains A or B (pA223, pA224, pA233, pA234).…”

“…A 258 251 P-motif related sequence TCAGTTAO is also present in SV40 domain B where its mutation is detrimental to enhancer activity (see Figure 2). The P-motif is duplicated in a variety of naturally occurring polyomavirus isolates and in mutants which are selected for growth in PCC4 teratocarcinoma cells (reviewed in Ruley and Fried, 1983;Melin et al, 1985), suggesting that it corresponds to an important element of the polyoma enhancer. Since a 26-bp polyoma virus segment which contains both the P-motif and the ElA-like enhancer motif acquires enhancer activity when polymerized (Veldman et al, 1985), it would be interesting to determine which of the two motifs (ElA-like or P-motif or both) of the polyoma virus domain A is functional in the chimeric SV40-polyomavirus enhancer.…”

“…Thus, the redundancy of enhancer motifs in SV40 may only be apparent if one assumes that some of the trans-acting factors are host-or cell-type specific, and that the ubiquitous activity of the SV40 enhancer is related to the multiplicity of its enhancer motifs. In this respect we note that the activity of the polyoma virus enhancer which lacks the Sph-motif and the duplication of the GT-motif, is restricted to certain cell types (see Ruley and Fried, 1983 for references), but that mutants active in some of these cells contain duplications of either polyoma virus enhancer domain A or B (reviewed in Ruley and Fried, 1983;Melin et al, 1985). Similarly, the cell-type specificity of the human polyomavirus JC is modified by multiplication of a GTmotif-like sequence (Miyamura et al, 1985).…”

A pancreas specificity results from the combination of polyomavirus and Moloney murine leukemia virus enhancer.

“…It appears that alterations in the B enhancer can display a tissue specificity for expression in certain lines of embryonal carcinoma cells (13)(14)(15). In addition to transcriptional regulation, the Py enhancers and also the heterologous immunoglobulin heavy-chain core enhancer regulate permissivity or tissue specificity of Py viral DNA replication (11,16), indicating that some linkage exists between tissuespecific DNA replication and transcription.…”

A Detailed Analysis Of Duplications Appearing During Early, High Multiplicity Infections With Polyoma Virus

“…Certain rearrangements within this region alter the host range of Py (Vasseur et al, 1982;Melin et al, 1985;Maione et al, 1985;De Simone & Amati, 1987). By dissecting the control region and by mutational analysis, the minimum length of genome sequence required for efficient replication of Py and SV40 has been defined.…”