DOT1L complex suppresses transcription from enhancer elements and ectopic RNAi in Caenorhabditis elegans.

Transcriptional control is mediated by interactions of transcription factors with their cognate DNA elements, as well as by epigenetic modifications to chromatin catalyzed by a variety of enzymes. Thus, understanding the crosstalk between transcription factors and epigenetic modifiers is of prime importance. The Dot1-like protein (DOT1L) is an evolutionary conserved methyltransferase with catalytic specificity towards histone 3 lysine 79 (H3K79). DOT1L is essential for mammalian development and has been studied mostly in the context of aggressive leukemias. Recent observations suggest that the role of DOT1L in malignant transformation can be generalized to contexts beyond leukemia. For instance, DOT1L has been implicated in breast cancer progression, and this has been attributed to its cooperation with c-Myc. However, the mechanistic details underlying this association are unknown. Previous work in our lab has shown that DOT-1.1, the C. elegans DOT1L homologue, is recruited to chromatin by ZFP-1 (similarly to DOT1L recruitment by AF10 in mammals), and this complex negatively modulates transcription. Interestingly, promoters of ZFP-1/DOT-1.1 target genes are enriched in E-boxes, the consensus binding motif for c-Myc. Prompted by the exciting hypothesis that DOT-1.1 and MML-1, the C. elegans c-Myc homologue, cooperate genome-wide, we profiled gene expression in wild-type worms and dot-1.1(gk105059), zfp-1(ok554), and mml-1(gk402844) loss-of-function mutants by microarray. We found significant overlaps between genes upregulated in the three mutants, and the same was observed for downregulated genes. A significant global increase of non-coding transcripts was observed in either mutant compared with wild-type. Therefore, ZFP-1/DOT-1.1 and MML-1 co-regulate both coding and non-coding genes and globally inhibit non-coding transcription. Further investigation is underway to uncover the mechanism of cooperation of ZFP-1/DOT-1.1 and MML-1. Profiling of gene expression in wild-type third larval stage (L3) larvae and zfp-1(ok554), dot-1.1(gk105059) and mml-1(gk402844) mutant worms.

Tiling_array_Fraser_elegans_N2

Unpublished C. elegans N2 Tiling array data. The data was analysed using TAS (version 1.1 Build 2, 5/10/2006) with probes originally mapped to WS150 version of the genome. Quantile normalization was carried out and probe intensity was median scaled.