Date Thesis Awarded

5-2022

Access Type

Honors Thesis -- Access Restricted On-Campus Only

Degree Name

Bachelors of Science (BS)

Department

Biology

Advisor

Lizabeth Allison

Committee Members

Jody Allen

Jennifer Rahn

Diane Shakes

Abstract

The thyroid hormone receptors, TR-a and TR-b, are transcription factors that regulate gene expression in response to thyroid hormone. The intracellular localization of TRs is a highly regulated process. TRs are primarily localized to the nucleus, but shuttle between the nucleus and cytoplasm. Prior research suggests that post-translational modification of TRs by acetylation plays a role in regulating this shuttling process, with acetylated TR having a more cytosolic localization than nonacetylated TR. This thesis research tested the hypothesis that the deacetylase HDAC3 is involved in this pathway. If HDAC3 is the enzyme involved, inhibition of this deacetylase would result in a more cytosolic localization of TR. To this end, RGFP966, an HDAC3 inhibitor, was introduced at various concentrations to HeLa (human) cells expressing green fluorescent protein (GFP)-tagged TR-a. This treatment was done to determine if HDAC3 inhibition had any effect on the intracellular localization of TR, as visualized by fluorescence microscopy, and if so, what concentration of RGFP966 best exemplifies these results. Results showed that HDAC3 inhibitor RGFP966 concentrations of 250-500 nM resulted in a more cytosolic localization of TR-a. In addition, GFP-TR-a1 expressing cells were also treated with AGK-2, an inhibitor of the deacetylase SIRT2, to investigate whether more than one deacetylase is involved in TR post-translational modification. When both RGFP966 and AGK-2 were compared at 250 nM, the results were slightly significant, thus suggesting that both HDAC3 and SIRT2 are involved in the deacetylation of TR. Understanding the mechanism of deacetylation of TR is key to understanding the inner-workings of regulating transcription of thyroid hormone responsive genes and may shed light on the molecular underpinnings of TR-related rare diseases.

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