# SV40 AND POLYOMA VIRUS TRANSFORMING PROTEINS

> **NIH NIH R01** · UNIVERSITY OF CALIFORNIA, SAN DIEGO · 1988 · $207,245

## Abstract

SV40 encodes two structurally related tumor (T) antigens, large T and small
T; polyoma virus encodes three related T antigens, large, medium and small
T.  Large T of either virus is a multifunctional protein involved in viral
DNA replication and in controlling transcription.  All tumor antigens are
implicated to some extent in malignant transformation, but SV40 large T and
polyoma virus medium T are most intimately involved in this process.  The
main goals of this proposal are:  (1) to investigate the possible role of
phosphorylation in the function(s) of SV40 large T.  We have previously
determined eight phosphorylation sites clustered in two separate regions of
large T.  It seems likely that the introduction of one or several negative
charges into the large T molecule will alter its function(s).  By studying
various mutants, defective in viral DNA replication, transcription control,
or transformation, we expect to establish correlations between mutant
defects and alterations in phosphorylation at individual sites.  Sites that
seem to be potentially important for functions will be removed by
site-directed mutagenesis, and the effect of the mutation of function will
be studied.  We also intend to investigate the kinetics of phosphorylation,
phosphate turnover at individual sites, and subcellular location of protein
kinases involved in phosphorylation of large T.  Furthermore, the effect of
phosphorylation on in vitro measurable activities or properties of large T,
such as DNA binding, ATPase activity, oligomerization, DNA synthesis, and
transcription will be investigated.  (2) to determine the phosporylation
sites in polyoma virus large T and to study their role in function.  We
suspect that certain phosphorylation sites have been conserved in evolution
because they are important for function.  (3) to investigate two proteins
(50.000 and 34.000 daltons) from SV40-transformed rat cells, precipitated
with antiserum against a synthetic peptide, corresponding to the carboxy
terminus of an alternate reading frame at the 3 prime end of the SV40 early
region.  We plan to examine whether these proteins are truly SV40-coded and
to study their properties.  (4) to purify polyoma virus medium T further
and to characterize its associated tyrosine-specific protein kinase
activity.  The kinase-active fraction of medium T sediments is 200K
complex.  The goal is to find out whether this complex is a tetramer of
medium T, or medium T associated with a cellular enzyme, and to understand
its role in transformation by polyoma virus.

## Key facts

- **NIH application ID:** 3173614
- **Project number:** 5R01CA036111-05
- **Recipient organization:** UNIVERSITY OF CALIFORNIA, SAN DIEGO
- **SAM.gov UEI:** UYTTZT6G9DT1
- **Principal Investigator:** GERNOT F WALTER
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 1988
- **Award amount:** $207,245
- **Award type:** 5
- **Project period:** 1983-12-01 → 1989-08-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/3173614

## Citation

> US National Institutes of Health, RePORTER application 3173614, SV40 AND POLYOMA VIRUS TRANSFORMING PROTEINS (5R01CA036111-05). Retrieved via MORVS 2026-10-25 from https://api.morvs.ai/grant/nih/3173614. Licensed CC0.

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