Missing links between histones and RNA Pol II arising from SAND?

Abstract

Correct deployment of developmental programs and maintenance of cell fates in eukaryotes rely on the timely activation or repression of gene expression. These processes depend to a large extent on modifications of chromatin structure that modulate the access of transcription factors to target DNA. In particular, Polycomb group (PcG) and trithorax group (trxG) chromatin remodeling complexes play key roles in depositing repressive and active histone marks, respectively, to maintain stable expression of developmental target genes. Yet despite enormous insights into both chromatin modification and transcription, the molecular mechanisms through which these two key processes influence each other are still quite nebulous. Recent independent studies from plant and human model systems have potentially uncovered a common ground for coordinating chromatin remodeling and transcriptional events. In this review, we discuss the function of the SAND domain proteins ULTRAPETALA1 (ULT1) and Aire as molecular links between chromatin remodelers and transcription effectors.