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R Schuurman

Publications and source records attributed to R Schuurman.

7 recordsLinked to original sources
PubMed1992

The 55 kDa regulatory subunit of protein phosphatase 2A plays a role in the activation of the HPV16 long control region in human cells with a deletion in the short arm of chromosome 11.

Previous results indicated that SV40 small t is essential for SV40-induced transformation of diploid cells but dispensable for the transformation of cells with a deletion on the short arm of chromosome 11 (del-11 cells). From these results we concluded that del-11 cells contain a cellular 'SV40 small t-like' factor, which is able to transactivate the HPV16 long control region (LCR) and to complement SV40 large T in transformation. Since SV40 small t and the regulatory 55 kDa subunit (PR55) of protein phosphatase 2A (PP2A), have been shown to inhibit the enzyme activity of PP2A, the PR55 beta subunit could be the putative 'small t-like' factor. In accordance with this hypothesis, we show that the PR55 beta subunit is highly expressed in del-11 but not in diploid cells and is able to trans-activate the HPV16 LCR in diploid cells. Moreover, inhibition of PP2A by okadaic acid resulted in trans-activation of the HPV16 LCR in diploid cells. Alignment of PR55 and SV40 small t showed a common four amino acid motif DKGG. We present evidence that the integrity of this motif is necessary for the PP2A-mediated ability of SV40 small t to trans-activate the HPV16 LCR.

Amino Acid Sequence↗
PubMed1992

Bovine polyomavirus, a cell-transforming virus with tumorigenic potential.

The early region of bovine polyomavirus (BPyV) was tested for its cell transformation potential employing an assay of dense focus formation. Dense foci of morphologically transformed cells were observed upon transfection of primary rodent cells with a plasmid construct encoding the complete early region of BPyV under the transcriptional control of the long terminal repeat of Rous sarcoma virus. No transformation of primary rodent cells was observed upon transfection of these cells with a plasmid encoding the complete early region of BPyV under the control of its own transcriptional regulatory sequences. In BPyV-transformed cells, the viral sequences had become integrated into the cellular genome, and expression of large T antigen could be detected in a high percentage of cells. The transformed cells were demonstrated to be capable of anchorage-independent growth and to be oncogenic in immunocompromised newborn rats. Therefore BPyV should be considered as a potentially tumorigenic polyomavirus. Since many commercial batches of calf serum have been shown to be contaminated with BPyV, our observations may have implications for the use of calf serum in cell culture.

Amino Acid Sequence↗
PubMed1992

Analysis of splice sites in the early region of bovine polyomavirus: evidence for a unique pattern of large T mRNA splicing.

The genetic organization of the early region of bovine polyomavirus (BPyV) was studied by analysis of the splice sites used in early mRNA maturation, using reverse transcription-polymerase chain reaction and DNA sequencing techniques. When compared to other polyomaviruses, the BPyV early region appears to have an uncommon organization. In the major early mRNA molecule two small intron sequences of 71 and 77 nucleotides, separated from one another by an 80 nucleotide exon sequence, were identified. Through splicing out both introns, a mRNA molecule is generated that contains an open reading frame with the capacity to encode 619 amino acids. Comparisons with the simian virus 40 large T antigen suggested that this mRNA molecule encodes the BPyV large T antigen. Remarkably, no mRNA product encoding a protein with a size comparable to that of the small t antigens of other polyomaviruses was detected. Another transcript was observed from which only the 77 nucleotide intron sequence had been removed, thereby creating a mRNA molecule with the capacity to encode only 45 amino acids. Whether this mRNA product represents a mature transcript which is translated in BPyV-infected cells or is an intermediate in the formation of the large T mRNA molecule is not known. Analysis of BPyV-specific early mRNA products isolated from BPyV-transformed murine cells revealed only the amplification product representing the putative large T antigen transcript.

Amino Acid Sequence↗
PubMed1991

Frequent detection of bovine polyomavirus in commercial batches of calf serum by using the polymerase chain reaction.

Twenty commercial batches of calf serum, obtained from several suppliers, were tested for the presence of bovine polyomavirus (BPyV) DNA and antibodies against the virus. Using polymerase chain reaction (PCR) technology, BPyV DNA was detected in 70% of the batches; no BPyV was detected in any of the negative control samples. The specificity of the amplification reactions was proven by hybridization. PCR results were confirmed by virus isolation experiments performed with five PCR-positive and five PCR-negative serum batches. The results indicate that the use of calf serum to supplement tissue culture media involves a serious risk of contaminating cell cultures with BPyV. No correlation was observed between the presence or absence of anti-BPyV immunoglobulins and the detection of BPyV-specific DNA sequences in the serum batches.

Animals↗
PubMed1990

The complete nucleotide sequence of bovine polyomavirus.

The complete sequence of the genome of bovine polyomavirus (BPyV), formerly known as the CK isolate of the stump-tailed macaque virus, is presented. The genomic organization of BPyV is similar to that of the non-rodent polyomaviruses. With a genome size of 4697 bp, BPyV has the smallest polyomavirus genome known so far. When compared to simian virus 40 (SV40), the shortness of the BPyV genome is due mainly to differences in the coding capacity of the BPyV early region. The first exon of the proposed large T antigen encodes only 35 amino acids; also, a coding region corresponding to the C-terminal 64 amino acids of the SV40 large T antigen is absent in BPyV. It is proposed that the nucleotide sequence encompassing the small t antigen coding sequence contains an intron sequence of 71 nucleotides. Together the two exon sequences encode a 124 amino acid protein. We conclude that this may be the first example of a polyomavirus that has a small t antigen which is translated from two exon sequences. The enhancer region of BPyV does not show homology to the SV40 enhancer sequences. An agnogene is present with a coding capacity of 118 amino acid residues. The highest degree of homology to SV40 and PyV is present in the VP1 molecule.

Amino Acid Sequence↗