roX RNAs Non-coding regulators of the male X chromosome in flies

The roX RNAs represent one of the paradigm examples of large non-coding RNAs involved in chromatin regulation. Interestingly, roX genes have a dual life. The RNA product is part of the MSL complex required for dosage compensation of the male X chromosome in Drosophila while the genomic location is used as a binding platform for MSL complex assembly. In this review we discuss both aspects of roX function and propose an integrated model for possible mechanisms how these RNAs might be involved in epigenetic regulation of the male X chromosome.