ROLE OF COREST N-TERMINAL EXTENSION ON LSD1/COREST DEMETHYLASE ACTIVITY

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Author:
Pecen, Turner John
Area of Honors:
Biochemistry and Molecular Biology
Degree:
Bachelor of Science
Document Type:
Thesis
Thesis Supervisors:
  • Song Tan, Thesis Supervisor
  • Joseph Reese, Honors Advisor
Keywords:
  • LSD1
  • CoREST
  • Demethylase
  • Nucleosome
  • Binding Assay
  • Activity Assay
  • Protein
  • Biochemistry
  • Molecular Biology
  • Complex
Abstract:
RNA transcription is partly controlled by epigenetic modifications to nucleosomes. Methylation of the histone tails can lead to either transcriptional silencing or activation depending on both the methylated residue and the degree of methylation. LSD1, lysine specific demethylase 1, acts to demethylate mono- and di- methylated H3K4. Demethylation of this residue leads to the silencing of genes otherwise activated when lysine 4 is methylated. LSD1 requires CoREST, a corepressor to target its nucleosomal substrate. A low resolution structure of LSD1-CoREST in complex with the nucleosome has been solved, but more experimentation is required to determine how CoREST and the nucleosomes interact. Solving this structure showed that the N-terminal extension of CoREST exists with multiple basic residues in close proximity to the extranucleosomal DNA. Alterations to the N-terminal extension could interfere with interactions with the extranucleosomal DNA. This would likely hinder the binding ability of the LSD1-CoREST complex and, by extension, its demethylase activity. I truncated and mutated the N-terminal extension to potentially interfere with interactions between the LSD1-CoREST complex and the nucleosome. Nucleosome binding assays and demethylase assays were performed to determine the changes in both binding and demethylase abilities resulting from these alterations. Understanding the result of these changes is necessary for refining the structural model and can also assist in determining areas for disrupting complex binding. This determination can also stand as making these targets for the treatment of cancer.