WILLIAM L. TAYLOR
ASSOCIATE PROFESSOR
EDUCATION:
B.S. 1975, Purdue University, West Lafayette, Indiana
Ph.D. 1982, Purdue University, West Lafayette, Indiana
Postdoctoral 1982-1985, Carnegie Institution of Washington, Baltimore, Maryland
RESEARCH INTERESTS: Our laboratory is involved in the study of the
developmental control of gene expression. The current model system used
in the laboratory is the TFIIIA gene of Xenopus laevis and the regulation
of this gene during early development.
The work on the developmental control of TFIIIA gene expression has centered
on the identification of cis-acting elements and trans-acting factors which
contribute to the high level of TFIIIA gene expression in Xenopus oocytes.
In these studies, the laboratory has used in vitro mutagenesis of TFIIIA
gene upstream sequences followed by reintroduction of the mutated gene into
oocytes at various stages or embryos by microinjection. Experiments have
defined many regulatory elements in the DNA sequences immediately upstream
from the mRNA initiation site of the TFIIIA gene. Three of these elements
are developmentally regulated and regulation occurs at two different developmental
times. One of the elements is a positive element which is active only in
immature oocytes. The other two developmentally regulated elements are
negative elements which are active only in somatic cells (embryos). All
of the developmentally regulated elements are of the type we expected, since
the TFIIIA gene is expressed at very high levels in immature oocytes, slightly
lower levels in mature oocytes and at extremely low levels in somatic cells.
We have also used various in vitro approaches to study DNA-protein interactions
within the upstream region of the TFIIIA gene in order to correlate DNA-protein
interactions with the expression and developmental regulation of the TFIIIA
gene. These studies have resulted in the molecular cloning of putative
cDNAs encoding the trans-acting factor which binds to the immature oocyte
specific cis-element which is described above. Using PCR approaches, we
have also obtained cDNA clones for another of the factors which contribute
to TFIIIA gene expression at all stages of development which is the Xenopus
homolog of USF, a well characterized mammalian transcription factor. Current
work in the lab involves verification of our putative cDNA clones as those
which encode the factors which control TFIIIA gene expression. These attempts
have included purification of the appropriate factors from immature oocytes
for sequencing and comparison to the cDNA sequences. Additionally, we are
attempting to use bacterially expressed protein in in vitro transcription
reactions and expression of the cDNAs in oocytes to ascertain the functionality
of the factors which we clone and/or purify.
Our studies of the TFIIIA gene have also led us to examine the role of
chromatin structure in the regulation of this gene. We have determined
that, in oocytes, a phased nucleosome in upstream region of the TFIIIA gene
activates the transcription of this gene. Both structural and functional
studies confirm the activation of the gene by this phased nucleosome. Studies
are underway to examine any changes in chromatin structure which may occur
in somatic cells and contribute to the repression of the TFIIIA gene in
somatic cells.
GRADUATE STUDENTS:
Vanderbilt University: Yu-Lian Fong, Ph.D., 1990; David Griffin, Ph.D.,
1994
CURRENT RESEARCH SUPPORT:
RO1GM39324 "TFIIIA Gene Expression in Oocytes and Somatic Cells"
4/1/92-3/31/96; $503,000
PUBLICATIONS:
Griffin, D., Dieter-Minth, C., and Taylor, W. (1994) Isolation and characterization
of the Xenopus laevis cDNA and genomic homologs of neuropeptide Y. Molecular
and Cellular Endocrinology, 101, 1-10.
Pfaff, S.L. and Taylor, W. (1992) Characterization of a Xenopus oocyte
factor that binds to a developmentally regulated cis-element in the TFIIIA
gene. Developmental Biology, 151, 306-316.
Pfaff, S.L., Hall, R.K., Hart, G.C., and Taylor, W. (1991) Regulation of
the Xenopus laevis transcription factor III A gene during oogenesis and
early embryogenesis: Negative elements repress the O-TFIIIA promoter in
embryonic cells. Developmental Biology, 145, 241-254.
Pfaff, S., Tamkun, M., and Taylor, W. (1990) pOEV: A Xenopus oocyte vector
that simplifies expression of genes by coupling transcription and translation.
Analytical Biochemistry, 188, 192-199.
Hall, R. and Taylor, W. (1989) Transcription factor IIIA gene espression
in Xenopus oocytes utilizes a transcription factor similar to the major
late transcription factor. Molecular and Cellular Biology, 9, 5003-5011.
Fong, Y-L., Taylor, W.L., Means, A.R., and Soderling, T.R. (1989) Studies
of the regulatory mechanism of Ca2+/calmodulin-dependent protein kinase
II. Journal of Biological Chemistry, 264, 16759-16763.
Taylor, W.L., Jackson, I.J., Siegel, N., Kumar, A., and Brown, D.D. (1986)
The developmental expression of the gene for TFIIIA in Xenopus laevis.
Nucleic Acids Research, 14, 6185-6195.
Taylor, W. (1983) Use of immobilized 5S-specific transcription factor for
the isolation of components of transcription complexes. Carnegie Institution
of Washington Yearbook, 83.
Taylor, W. and Jackson, I. (1983) Isolation of the gene encoding 5S-specific
transcription factor. Carnegie Institution of Washington Yearbook, 83.
Argos, P., Taylor, W.L., Minth, C.D., and Dixon, J.E. (1983) Nucleotide
and amino acid sequence comparisons of preprosomatostatins. Journal of
Biological Chemistry, 258, 8788-8793.
Dixon, J.E, Andrews, P.C., Collier, K., Deschenes, R., Funckes, C., Lorenz,
L., Magazin, M., Minth, C.D., Nichols, R., Tavianini, M., Taylor, W., Weith,
H.L., Aron, D.C., Birmbaum, R.S., Muszynski, M., and Roos, B.A. (1983)
Cloning and biosynthetic studies of rat somatostatin. Scandinavian Journal
of Gastroenterology, 18, 25-31.
Taylor, W.L., Collier, K.J., Deschennes, R., Andrews, P.C., Minth, C.D.,
Weith, H.L., and Dixon, J.E. (1983) Biosynthetic studies on the hypothalamic
releasing hormones. In E.C. Griffiths and G.W Bennett (Eds.), Thyrotropin
Releasing Hormone. Raven Press.
Minth, C.D., Taylor, W.L., Magazin, M., Tavianini, M.A., Collier, K., Weith,
H.L., and Dixon, J.E. (1982) The structure of cloned DNA complementary to
catfish pancreatic somatostatin-14 messenger RNA. Journal of Biological
Chemistry, 257, 10372-10377.
Taylor, W.L., Collier, K.J., Deschenes, R.J., Weith, H.L., and Dixon, J.E.
(1981) Sequence analysis of a cDNA coding for a pancreatic precursor to
somatostatin. Proceedings of the National Academy of Sciences USA,
78, 6694-6698.