Related Experiment Videos
Comparison of the DNA binding specificity and function of v-ErbA and thyroid hormone receptor alpha 1
1Division of Endocrinology and Metabolism, University of Michigan Medical Center, Ann Arbor 48109-0678, USA.
Abstract:
The oncoprotein v-ErbA is a mutated version of thyroid hormone receptor alpha 1. Although the basis for the oncogenic action of v-ErbA is unknown, expression of this protein is known to inhibit thyroid hormone and retinoic acid induction of target genes. The DNA binding domain of v-ErbA differs from that of thyroid hormone receptor alpha 1 in two amino acids felt to be crucial for determining the specificity of DNA binding. However, the DNA binding properties of v-ErbA have not been examined independent of a comparison of binding to already known thyroid hormone response elements. In the current studies a non-biased strategy was used to select from a pool of random DNA those sequences that bind v-ErbA with high affinity. The highest affinity binding sequence was identified as the decamer 5'-T(A/G)AGGTCACG, which is closely related to the optimal thyroid hormone receptor alpha 1 binding sequence, TAAG-GTCA. Transfection studies demonstrate that among equal thyroid hormone responsive elements, those that contain the optimal v-ErbA consensus will be repressed by v-ErbA in preference to those that do not. These studies indicate that v-ErbA and thyroid hormone receptor alpha 1 regulate overlapping sets of response elements, and that all sequences that are highly responsive to thyroid hormone are not necessarily responsive to v-ErbA.
Insights
The oncoprotein v-ErbA binds DNA sequences distinct from thyroid hormone receptor alpha 1. This binding preference influences gene repression, revealing insights into v-ErbA
Area of Science:
- Molecular Biology
- Oncology
- Endocrinology
Background:
- The oncoprotein v-ErbA is a mutated form of thyroid hormone receptor alpha 1.
- v-ErbA inhibits gene induction by thyroid hormone and retinoic acid, but its oncogenic mechanism is unclear.
- v-ErbA's DNA binding domain differs from thyroid hormone receptor alpha 1, potentially altering DNA binding specificity.
Purpose of the Study:
- To investigate the DNA binding properties of v-ErbA independently of known response elements.
- To identify high-affinity DNA sequences recognized by v-ErbA.
- To compare the DNA binding and regulatory roles of v-ErbA and thyroid hormone receptor alpha 1.
Main Methods:
- Utilized a non-biased strategy to select DNA sequences with high v-ErbA binding affinity from a random pool.
- Identified the optimal v-ErbA binding sequence using DNA selection and sequencing.
- Performed transfection studies to assess the impact of v-ErbA binding on gene repression.
Main Results:
- The highest affinity v-ErbA binding sequence was identified as 5'-T(A/G)AGGTCACG, closely related to the thyroid hormone receptor alpha 1 binding sequence.
- v-ErbA preferentially represses target genes containing its optimal consensus binding sequence.
- v-ErbA and thyroid hormone receptor alpha 1 regulate overlapping, but not identical, sets of DNA response elements.
Conclusions:
- v-ErbA and thyroid hormone receptor alpha 1 bind to overlapping DNA response elements.
- v-ErbA's distinct DNA binding preference influences its oncogenic activity through differential gene repression.
- Not all thyroid hormone-responsive elements are equally responsive to v-ErbA.