HMCES modulates the transcriptional regulation of nodal/activin and BMP signaling in mESCs

Despite the fundamental roles of TGF-β family signaling in cell fate determination in all metazoans, the mechanism by which these signals are spatially and temporally interpreted remains elusive. The cell-context-dependent function of TGF-β signaling largely relies on transcriptional regulation by SMAD proteins. Here, we discover that the DNA repair-related protein, HMCES, contributes to early development by maintaining nodal/activin- or BMP-signaling-regulated transcriptional network. HMCES binds with R-SMAD proteins, co-localizing at active histone marks. However, HMCES chromatin occupancy is independent on nodal/activin or BMP signaling. Mechanistically, HMCES competitively binds chromatin to limit binding by R-SMAD proteins, thereby forcing their dissociation and resulting in repression of their regulatory effects. In Xenopus laevis embryo, hmces KD causes dramatic development defects with abnormal left-right axis asymmetry along with increasing expression of lefty1. These findings reveal HMCES transcriptional regulatory function in the context of TGF-β family signaling. [Display omitted] •HMCES-KO impairs ESCs pluripotency and alters TGF-β family transcriptional network•HMCES interacts with R-SMADs and co-occupies with active histone marks•HMCES competitive binding to chromatin drives dissociation of R-SMADs•Hmces deficiency impairs Xenopus laevis embryo development Liang et al. discover that the DNA repair-related protein, HMCES, contributes to early development by maintaining a nodal/activin- or BMP-signaling-regulated transcriptional network. HMCES competitively binds chromatin to limit binding by R-SMAD proteins, resulting in repression of their regulatory effects. This reveals HMCES transcriptional regulatory function in TGF-β family signaling.