Orchestrating Asymmetric Expression: Mechanisms behind Regulation.

Compensation for the gene dosage disequilibrium between sex chromosomes in mammals is achieved in female cells by repressing one of its X chromosomes through a process called X chromosome inactivation (XCI), exemplifying the control of gene expression by epigenetic mechanisms. A critical player in this mechanism is , a long, non-coding RNA upregulated from a single X chromosome during early embryonic development in female cells. Over the past few decades, many factors involved at different levels in the regulation of have been discovered. In this review, we hierarchically describe and analyze the different layers of regulation operating concurrently and intricately interacting with each other to achieve asymmetric and monoallelic upregulation of in murine female cells. We categorize these into five different classes: DNA elements, transcription factors, other regulatory proteins, long non-coding RNAs, and the chromatin and topological landscape surrounding .