Development

Controlling Sex

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Science  08 Jul 2011:
Vol. 333, Issue 6039, pp. 137
DOI: 10.1126/science.333.6039.137-b

Chromosomes are packaged into transcriptionally silent heterochromatin and transcriptionally active euchromatin. The highly conserved protein HP1a marks heterochromatin in Drosophila, and heterochromatin-rich telomeres are capped by a protein complex composed of HP1a and HP1/ORCAssociated Protein (HOAP). Because knockdown of HP1a is associated with loss of male viability, and the HP1a-HOAP complex shows similarity to the mammalian sex-determining region of the Y chromosome (SRY), Li et al. sought to investigate the role of this complex in regulating sex determination in Drosophila. The authors carried out gene expression analysis in HOAP-deficient flies and found that the majority of down-regulated genes were those associated with the testis. Further analyses showed that this was due to repressive activity by HOAP and both repressive and activating functions of HP1a that affected the function of the establishment promoter of Sex-lethal, the master regulator of sex determination. Flies mutant in HP1a or HOAP exhibited defects in sex determination. Thus, proteins typically associated with heterochromatin are critical for regulating the changes in gene expression required for sex determination in flies.

PLoS Genet. 7, e1002122 (2011).

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