The N-terminal domain of Sxl protein disrupts Sxl autoregulation in females and promotes female-specific splicing of tra in males.
Sex determination in Drosophila depends upon the post-transcriptional regulatory activities of the Sex-lethal (Sxl) gene. Sxl maintains the female determined state and activates female differentiation pathways by directing the female-specific splicing of Sxl and tra pre-mRNAs. While there is compelling evidence that Sxl proteins regulate splicing by directly binding to target RNAs, previous studies indicate that the two Sxl RNA-binding domains are not in themselves sufficient for biological activity and that an intact N-terminal domain is also critical for splicing function. To further investigate the functions of the Sxl N terminus, we ectopically expressed a chimeric protein consisting of the N-terminal 99 amino acids fused to ss-galactosidase. The Nss-gal fusion protein behaves like a dominant negative, interfering with the Sxl autoregulatory feedback loop and killing females. This dominant negative activity can be attributed to the recruitment of the fusion protein into the large Sxl:Snf splicing complexes that are found in vivo and the consequent disruption of these complexes. In addition to the dominant negative activity, the Nss-gal fusion protein has a novel gain-of-function activity in males: it promotes the female-specific processing of tra pre-mRNAs. This novel activity is discussed in light of the blockage model for the tra splicing regulation.
Deshpande
G
G
Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA. gdeshpande@molbio.princeton.edu
Calhoun
G
G
Schedl
P D
PD
D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics*; D004330:Drosophila / Q000196:embryology* / Q000235:genetics; D029721:Drosophila Proteins; D029968:Escherichia coli Proteins; D005260:Female; D018507:Gene Expression Regulation, Developmental; D005799:Genes, Dominant; D005804:Genes, Lethal; D019476:Insect Proteins / Q000378:metabolism; D008297:Male; D012322:RNA Precursors / Q000235:genetics; D012323:RNA Processing, Post-Transcriptional; D012326:RNA Splicing / Q000235:genetics*; D012333:RNA, Messenger / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000235:genetics*; D011993:Recombinant Fusion Proteins / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D019849:Sex Determination Processes; D019076:Transgenes; D001616:beta-Galactosidase / Q000235:genetics
D001426:Bacterial Proteins; D029721:Drosophila Proteins; D029968:Escherichia coli Proteins; D019476:Insect Proteins; D012322:RNA Precursors; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D011993:Recombinant Fusion Proteins; C067777:Sxl protein, Drosophila; C067119:kilA protein, E coli; D001616:beta-Galactosidase