Somatic inactivation leads to slow, canonical DNA methylation loss in murine hematopoietic cells.

Mutations in the gene encoding DNA methyltransferase 3A () are the most common cause of clonal hematopoiesis and are among the most common initiating events of acute myeloid leukemia (AML). Studies in germline and somatic knockout mice have identified focal, canonical hypomethylation phenotypes in hematopoietic cells; however, the kinetics of methylation loss following acquired inactivation in hematopoietic cells is essentially unknown. Therefore, we evaluated a somatic, inducible model of hematopoietic loss, and show that inactivation of in murine hematopoietic cells results in a relatively slow loss of methylation at canonical sites throughout the genome; in contrast, remethylation of Dnmt3a deficient genomes in hematopoietic cells occurs much more quickly.

Remethylation of hematopoietic cells is associated with partial correction of gene dysregulation and reduced myeloid skewing.

Mutations in the DNA methyltransferase 3A () gene are the most common cause of age-related clonal hematopoiesis (ARCH) in older individuals, and are among the most common initiating events for acute myeloid leukemia (AML). The most frequent mutation in AML patients (R882H) encodes a dominant-negative protein that reduces methyltransferase activity by ∼80% in cells with heterozygous mutations, causing a focal, canonical DNA hypomethylation phenotype; this phenotype is partially recapitulated in murine bone marrow cells. To determine whether the hypomethylation phenotype of hematopoietic cells is reversible, we developed an inducible transgene to restore expression of in transplanted bone marrow cells from mice.

PML-RARA requires DNA methyltransferase 3A to initiate acute promyelocytic leukemia.

The DNA methyltransferases DNMT3A and DNMT3B are primarily responsible for de novo methylation of specific cytosine residues in CpG dinucleotides during mammalian development. While loss-of-function mutations in DNMT3A are highly recurrent in acute myeloid leukemia (AML), DNMT3A mutations are almost never found in AML patients with translocations that create oncogenic fusion genes such as PML-RARA, RUNX1-RUNX1T1, and MLL-AF9. Here, we explored how DNMT3A is involved in the function of these fusion genes.

Conversion of the LIN-1 ETS protein of Caenorhabditis elegans from a SUMOylated transcriptional repressor to a phosphorylated transcriptional activator.

The LIN-1 ETS transcription factor plays a pivotal role in controlling cell fate decisions during development of the Caenorhabditis elegans vulva. Prior to activation of the RTK/Ras/ERK-signaling pathway, LIN-1 functions as a SUMOylated transcriptional repressor that inhibits vulval cell fate. Here we demonstrate using the yeast two-hybrid system that SUMOylation of LIN-1 mediates interactions with a protein predicted to be involved in transcriptional repression: the RAD-26 Mi-2β/CHD4 component of the nucleosome remodeling and histone deacetylation (NuRD) transcriptional repression complex.

Essential elements of a licensed, mammalian plasmid origin of DNA synthesis.

We developed a mammalian plasmid replicon with a formerly uncharacterized origin of DNA synthesis, 8xRep*. 8xRep* functions efficiently to support once-per-cell-cycle synthesis of plasmid DNA which initiates within Rep*. By characterizing Rep*'s requirements for acting as an origin, we have uncovered several striking properties it shares with DS, the only other well-characterized, licensed, mammalian plasmid origin of DNA synthesis.

Sumoylation of LIN-1 promotes transcriptional repression and inhibition of vulval cell fates.

The LIN-1 ETS transcription factor inhibits vulval cell fates during Caenorhabditis elegans development. We demonstrate that LIN-1 interacts with UBC-9, a small ubiquitin-related modifier (SUMO) conjugating enzyme. This interaction is mediated by two consensus sumoylation motifs in LIN-1.