by Franziska Turck
Research Group Leader
Max Planck Institue for Plant Breeding Research
Polycomb group repressive protein complexes (PRCs) are essential for transcriptional regulation in higher eukaryotes; they act through the establishment of repressive epigenetic marks at specific chromatin regions. A key research question remains how PRC complexes find their target regions. In Drosophila, PRC2, responsible for establishing H3K27me3, is recruited via several well described motifs present in Polycomb response elements (PREs). In mammals, PREs and associated motifs are less obvious, while PRC recruitment through long non-coding RNAs has gathered much attention. In plants, until recently, PRC recruitment by cis-elements or non-coding RNA was not described with the exception of a few case studies.
I will present evidence for general mechanisms of PRC1 and PRC2 recruitment by B3 domain transcription factors and TELOMERE REPEAT BINDING FACTORs (TRBs), respectively. RY-motifs and teloboxes, the cognate elements of these DNA-binding protein classes, distribute along H3K27me3 marked regions with a high likelihood of presence in gene bodies. Approximately a fifth of PcG target genes depends on the joint action of TRBs and PRC2 for H3K27me3 coverage and transcriptional repression, these genes are particularly enriched in teloboxes but relatively depleted in RY-motifs. In contrast, genes enriched for RY-motifs but depleted for teloboxes gain H3K27me3 in trb mutants suggesting that these motifs compete for enzymatic activities that stabilize H3K27me3. In conclusion, plant PREs appear to be discontinuous and composed of a set of motifs that act in partial redundancy allowing for a concerted regulation of distinct groups of Polycomb target genes.
Zhou Y, Wang Y, Krause K, Yang T, Dongus JA, Zhang Y, Turck F.
Nat Genet. 2018 May;50(5):638-644. doi: 10.1038/s41588-018-0109-9.
Oka R, Zicola J, Weber B, Anderson SN, Hodgman C, Gent JI, Wesselink JJ, Springer NM, Hoefsloot HCJ, Turck F, Stam M.
Genome Biol. 2017 Jul 21;18(1):137. doi: 10.1186/s13059-017-1273-4.
Zhou Y, Tergemina E, Cui H, Förderer A, Hartwig B, Velikkakam James G, Schneeberger K, Turck F.
Proc Natl Acad Sci U S A. 2017 May 2;114(18):4833-4838. doi: 10.1073/pnas.1620955114. Epub 2017 Apr 20.
Zhou Y, Romero-Campero FJ, Gómez-Zambrano Á, Turck F, Calonje M.
Genome Biol. 2017 Apr 12;18(1):69. doi: 10.1186/s13059-017-1197-z.