Graduation Year


Document Type

Open Access Senior Thesis

Degree Name

Bachelor of Arts



Second Department


Reader 1

Emily Wiley

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© 2017 Claire Bagnani


In the nucleus, post-translational modifications on histone N-terminal tails can determine how local DNA is packaged. In one case, T. thermophila proteins Hhp1, Hpl1, and Hpl2, all related to the Heterochromatin Protein 1 (HP1) family, are associated with heterochromatin and thus gene silencing. They may do this by binding to trimethylated lysine 9 and lysine 27, located on the tail of histone H3. One distinct region of these proteins, the chromodomain (CD), may bind these marks, while another region, the chromoshadow domain (CSD) homodimerizes to interact with other proteins. This study explores what effect, if any, the CSD has on the CD’s ability to localize to chromatin bodies marked by these post-translational modifications on the tail of H3. GFP tagged chromoshadow domain deficient Hhp1, Hpl1, and Hpl2 were overexpressed in T. thermophila cells and the localization of these proteins to chromatin bodies in the macronuclei during vegetative growth or developing macronuclei during conjugation was assessed using fluorescence microscopy. The retention of the trimethylated lysine 27 mark was also assessed in cells expressing CSD deficient Hhp1 using immunofluorescence microscopy. The results suggest that the chromoshadow domains of all proteins disrupt typical wild type localization patterns to different degrees. The CSD of Hpl2 seems to have more of an effect on localization than the CSD of Hhp1 and Hpl1.

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