1. The Curious Case of Bivalent Marks
Hans-Martin Herz, Shima Nakanishi, Ali Shilatifard 
Developmental Cell 
Volume 17, Issue 3, Pages (September 2009)
DOI: /j.devcel
Copyright © 2009 Elsevier Inc. Terms and Conditions

2. Figure 1 Transcriptional Regulation and Chromatin Modifications
(A) RNA polymerase II and its basal transcription machinery initiate transcription. The macromolecular complex COMPASS, containing the Set1 and/or MLL1–4 proteins, marks active chromatin by trimethylation on lysine 4 of histone H3 (K4me3) (green spheres).
(B) Transcriptionally repressed regions of chromatin are marked by trimethylation on lysine 27 of histone H3 (K27me3) (red spheres through PRC2), which can recruit the PRC1 complex, resulting in repression.
(C) In mammalian ES cells, developmentally regulated genes are marked by histone H3 trimethylation on both H3K4 and H3K27, a state known as bivalent.
(D) In this issue of Developmental Cell, Akkers et al. demonstrate that Xenopus tropicalis transitions through early development without the requirement for bivalently marked promoters.
Developmental Cell  , DOI: ( /j.devcel )
Copyright © 2009 Elsevier Inc. Terms and Conditions