Graduation Year

Spring 2012

Document Type

Open Access Senior Thesis

Degree Name

Bachelor of Arts

Department

Biology

Reader 1

Emily A. Wiley

Reader 2

Bryan Thines

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Terms of Use for work posted in Scholarship@Claremont.

Rights Information

© 2012 T. Alexandria Dumas

Abstract

During S phase of the cell cycle, newly synthesized histones are acetylated in the cytoplasm in patterns specific to DNA replication. Once incorporated into nucleosomes, these histones are rapidly deacetylated by enzymes known as histone deacetylases. Though common in all organisms, the significance of this molecular mechanism is not fully understood. Homologous to HDAC6 in humans and HDA1 in budding yeast, Tetrahymena histone deacetylase 2 (Thd2) has been identified as the only known histone deacetylase that performs this task in the unicellular eukaryote Tetrahymena thermophila. Localizing to the transcriptionally inactive germline nucleus, the micronucleus, Thd2 has been found to deacetylate histones H3 and H4 at K9 and/or K14. In order to gain further insight into the role of deposition-related deacetylation in chromatin maturation, the micronuclear morphology and modification status of H3K27, a known marker for heterochromatin in several eukaryotes, were examined in both vegetative and synchronized complete Δthd2 mutant cells. Immunofluorescence microscopy, DAPI staining and a western blot analysis revealed abnormal phenotypes and the conservation of H3K27 methylation in the absence of Thd2. These findings further indicate a role for Thd2 in the maintenance of chromatin structure and suggest the possibility of another mechanism required for deacetylation at H2K27. Essentially, this demonstrates the importance of deposition-related histone deacetylation in chromatin maturation after DNA replication and further maintenance of chromatin domains.

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