<p>DNA methylation is an epigenetic modification that is nearly ubiquitous.
Eukaryotic DNA methylation contributes to the regulation of gene expression and
maintaining genome integrity. In mammals, DNA methylation occurs primarily on
the C5 carbon of cytosine in a CpG dinucleotide context and is catalyzed by the
DNA methyltransferases, DNMT1, DNMT3A and DNMT3B. While <i>dnmt3a</i>
and <i>dnmt3b</i> genes are highly
homologous, the enzymes have distinct functions. Some previous reports
suggested differences in the enzymatic behavior of DNMT3A and 3B, which could
affect their biological roles. The goal of my thesis work was to characterize kinetics
mechanisms of DNMT3A and 3B, and to identify the similarities and differences
in their catalytic properties that contribute to their distinct biological
functions. Given the sequence similarity between the enzymes, we asked whether
DNMT3B was kinetically similar to DNMT3A. In a series of experiments designed
to distinguish between various kinetics mechanisms, we reported that unlike
DNMT3A, DNMT3B methylated tandem CpG on DNA in a processive manner. We also
reported that the disruption of the R-D interface, critical for the
cooperativity of DNMT3A, had no effect on DNMT3B activity, supporting the
non-cooperative mechanism of this enzyme. </p>
<p>DNMT3A is frequently mutated in numerous cancers. Acute Myeloid Leukemia
(AML) is a malignancy of hematopoietic stem cells in which numerous patients
exhibit a high frequency of the heterozygous somatic mutation Arg882His in
DNMT3A. Through thorough consensus motif building, we discovered a strong
similarity in CpG flanking sequence preference between DNMT3A Arg882His variant
and DNMT3B enzyme. Moreover, we found that the variant enzyme has the same kinetics
mechanism as DNMT3B, indicating a gain-of-function effect caused by the
mutation. This change is significant because the variant enzyme can aberrantly
methylate DNMT3B targets in AML cells and effect global gene expression. In particular,
given that DNMT3B has been shown to have oncogenic properties, this suggests
that the Arg882His variant can acquire similar oncogenic properties and drive
AML development.</p>
<p>Taken together, my thesis work provides novel insights into the
relationship between the biochemical properties and the biological functions of
DNMT3A and 3B. </p>
| Identifer | oai:union.ndltd.org:purdue.edu/oai:figshare.com:article/12805529 |
| Date | 14 August 2020 |
| Creators | Allison B Norvil (9010811) |
| Source Sets | Purdue University |
| Detected Language | English |
| Type | Text, Thesis |
| Relation | https://figshare.com/articles/thesis/Biochemical_Investigation_of_the_de_novo_DNA_Methyltransferases_DNMT3A_and_DNMT3B/12805529 |
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