Clues to a riddle in dosage compensation

Marnie Gelbart and Mitzi Kuroda published findings in Nature Structural Biology that address a riddle in chromosomal dosage compensation during X inactivation.  They show that while the male-specific lethal (MSL) complex itself only localizes to a fraction of active genes on the male X chromosome, the end result of MSL activity (H4 Lys16 acetylation), is seen on all actively transcribed regions.  Their results indicate that the interaction of the MSL complex with affected sites is short lived and may occur through spreading of the complex on the chromosome or looping of intervening regions.