TSH-B GENE EXPRESSION AND REGULATION BY TH

Project Details

Description

Thyrotropin (TSH) is composed of two subunits: an alpha subunit, common to
pituitary TSH and pituitary and placental gonadotropins, and a unique bet
subunit (TSHbeta). Thyroid hormone and its nuclear receptor (c-erbA) bind
to and regulate the transcription of a variety of genes including both TSH
subunit genes (TSHalpha, TSHbeta) and the rat growth hormone gene (rGH).
However, the molecular mechanisms that determine whether a thyroid hormone
DNA response element (TRE) negatively (e.g., TSHbeta) or positively (e.g.,
rGH) regulates gene expression are completely unknown. The proposed
studies will determine whether the location, orientation, or a specific DNA
sequence defines a TRE as inhibitory or stimulatory. DNA transfection
studies in a variety of cell lines will be performed using chimeric
constructs containing inhibitory and stimulatory TREs in a variety of
locations and orientations. Moreover, since preliminary evidence suggests
that an additional nuclear protein(s), other than the thyroid hormone
receptor, is involved in the molecular mechanism of thyroid hormone
inhibition of human TSHbeta expression (hTSHbeta) an additional goal of
these studies will be to define further the cis-acting elements to which
this protein(s) binds, and whether it is cell-specific. DNA transfection
studies using deletions and mutations of the human TSHbeta TRE in parallel
with DNase I footprinting studies of this TRE with nuclear extracts from
TSH-secreting and non-secreting cell lines and tissues will be utilized to
accomplish this goal. These studies will provide new insight into thyroid
hormone action and allow a more detailed model of thyroid hormone action at
any TRE to be developed.

Since additional nuclear proteins in the thyrotroph may be involved in the
molecular mechanism of thyroid hormone inhibition of hTSHbeta expression,
the second major goal of these studies will be to define cis-acting
elements responsible for thyroid hormone regulation and thyrotroph-specific
expression of the hTSHbeta gene. To accomplish this goal, in vitro DNA
transfection studies (utilizing chimeric hTSHbeta constructs) and DNA
binding assays (DNase I footprinting) will be correlated with in vivo
expression of chimeric hTSHbeta genes in transgenic mice. The long range
goal of these studies is to determine the interrelationship between cell-
specific expression and thyroid hormone regulation of the hTSHbeta gene in
the anterior pituitary. Ultimately, a greater understanding of thyroid
hormone action in man may be gained.
StatusFinished
Effective start/end date9/17/925/31/96

Funding

  • National Institute of Diabetes and Digestive and Kidney Diseases
  • National Institute of Diabetes and Digestive and Kidney Diseases
  • National Institute of Diabetes and Digestive and Kidney Diseases
  • National Institute of Diabetes and Digestive and Kidney Diseases

ASJC

  • Genetics
  • Molecular Biology

Fingerprint

Explore the research topics touched on by this project. These labels are generated based on the underlying awards/grants. Together they form a unique fingerprint.