Equalizing the sexes

Two independent research papers in the February 1 issue of G&D reveal that the Drosophila UNR protein is a novel regulator of X-chromosome dosage compensation in flies. Dosage compensation is the equalization of X-linked gene expression between males (which have one X chromosome in flies) and females (which have two X chromosomes in flies). Fruit flies accomplish this by increasing transcription of the single male X chromosome two-fold. Transcriptional upregulation of the Dros. male X chromosome is facilitated by the Dosage Compensation Complex (DCC). The DCC fails to assemble in female flies because a key subunit, male-specific lethal 2 (msl-2), is not produced.

Previous work identified the sex-lethal protein (dSXL) as a necessary repressor of msl-2 translation. New work from the labs of Drs. Fatima Gebauer (CRG-UPF) and Matthias Hentze (EMBL) identify the Drosophila homolog of the mammalian UNR protein as a co-factor required for SXL-mediated repression of msl-2 translation.

Dr. Gebauer points out that the “UNR is, therefore, an essential component of a translational control mechanism that prevents dosage compensation in female cells,” and Dr. Hentze adds that “These new studies teach us how a protein that is expressed in both sexes can be used for an essential female-specific function. Learning more about how dSXL and UNR work together will instruct us on how cells control the key step of protein synthesis.”