Characterization of the interaction between MIER1β and lysine 27 of Histone 3

Abstract

Acetylation (ac) and tri-methylation (me3) of lysine number 27 on histone 3 (H3K27) play a very important role for early development and differentiation in embryonic stem cells, and often determine which cell type- specific processes are silenced and activated. H3K27 marked genes are often aberrantly expressed in adult cancers. When H3K27 is tri-methylated (H3K27me3), it is an indicator for a transcriptionally inactive gene. When H3K27 is acetylated (H3K27ac), it is an indicator for a transcriptionally active gene. This study focused on determining the binding site for H3K27ac within the mesoderm induction early response 1 (MIER1) protein, a fibroblast growth factor (FGF) inducible early response gene that is known to recruit chromatin modifiers and transcription factors for gene repression. The first 83 amino acids of MIER1 had been previously shown to bind H3K27ac. Alignment verification of the first 83 amino acids of MIER1 between different species revealed highly conserved sequences that represent the potential binding site. Site directed mutagenesis was employed to mutate highly conserved hydrophobic aromatic amino acid sequences in the full-length protein, as well as create deletion constructs. The mutated MIER1 proteins were then tested against wild type MIER1 protein for their ability to bind H3K27ac in peptide pull down assays. The results of this study have localized the C-terminal end of the 83 amino acid binding site to amino acids 36-50, and have shown that the amino acid sequence ³⁸TLE⁴⁰ is required in part for binding.