Characterization of histone modifying enzymes and their substrates in maize

Doctoral Thesis / Dissertation from the year 2007 in the subject Chemistry - Bio-chemistry grade: Doctorate University of Innsbruck (Institute of Molecular Biology) language: English abstract: The maize ZmHda1 is a class II HDA1-like histone deacetylase. ZmHda1 has been purified to homogeneity and found to be a 48 kDa monomeric protein (Brosch et al. 1996a). However ZmHda1 specific antibodies can detect two other protein bands of molecular sizes of 84 and 65 kDa on immunoblots indicating that ZmHda1 exists natively in different molecular forms. These two protein forms of ZmHda1 are found in protein complexes of high molecular weights and they are enzymatically inactive (Pipal et al. 2003). Attempts to identify the protein components of the ZmHda1 protein complexes have been made. The second part of this study showed that histone methylation profile in maize embryos quantitatively and qualitatively changes as the germination progresses from 0 to 72 h. The total and chromatin unbound HMT activity decrease during the germination progress while the chromatin bound HMT activity increases. This increase was most remarkable as an increase in methylation of H4K20 residue and to a lesser extent in mono- and tri- methylated H3K9 and dimethylated H3K36. With the progress of germination the decrease in dimethylated H3K9 was remarkable. The decrease in H3K4 methylation and dimethylated H4R3 was less pronounced. Seven different histone methyltransferase activities could be separated from the 72h maize embryos; three of them were chromatin bound and four were found soluble in the cytoplasmic extract. Two of the chromatin bound activities AI and AII2 methylate histone H3. AII2 showed H3K9 specificity and has a molecular size of 67 kDa. The third chromatin bound HMT activity AII1 has a molecular size of 120 kDa and is H4 specific. Purification schemes could not yield purification of these activities to homogeneity; however LC-MS/MS analysis of a chromatographic fractio