Abnormal Dosage Compensation of Reporter Genes Driven by the Drosophila Glass Multiple Reporter (GMR) Enhancer-Promoter

In Drosophila melanogaster the male specific lethal (MSL) complex is required for upregulation of expression of most X-linked genes in males, thereby achieving X chromosome dosage compensation. The MSL complex is highly enriched across most active X-linked genes with a bias towards the 3′ end. Previous studies have shown that gene transcription facilitates MSL complex binding but the type of promoter did not appear to be important. We have made the surprising observation that genes driven by the glass multiple reporter (GMR) enhancer-promoter are not dosage compensated at X-linked sites. The GMR promoter is active in all cells in, and posterior to, the morphogenetic furrow of the developing eye disc. Using phiC31 integrase-mediated targeted integration, we measured expression of lacZ reporter genes driven by either the GMR or armadillo (arm) promoters at each of three X-linked sites. At all sites, the arm-lacZ reporter gene was dosage compensated but GMR-lacZ was not. We have investigated why GMR-driven genes are not dosage compensated. Earlier or constitutive expression of GMR-lacZ did not affect the level of compensation. Neither did proximity to a strong MSL binding site. However, replacement of the hsp70 minimal promoter with a minimal promoter from the X-linked 6-Phosphogluconate dehydrogenase gene did restore partial dosage compensation. Similarly, insertion of binding sites for the GAGA and DREF factors upstream of the GMR promoter led to significantly higher lacZ expression in males than females. GAGA and DREF have been implicated to play a role in dosage compensation. We conclude that the gene promoter can affect MSL complex-mediated upregulation and dosage compensation. Further, it appears that the nature of the basal promoter and the presence of binding sites for specific factors influence the ability of a gene promoter to respond to the MSL complex

The importance of the promoter in Drosophila dosage compensation : a thesis presented in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Genetics at Massey University, Palmerston North, New Zealand

Dosage compensation is the equalisation of gene expression from unequal doses of genes. Drosophila males up-regulate transcription from their single X chromosome to equal that from the two female X chromosomes. Five malespecific lethal (msl) genes are required in males, and encode the main agents of the up-regulation. At least these proteins, together with either or both of two noncoding RNAs, form the MSL chromatin-modifying complex. Female-specific translational repression of a key component, msl2, limits the complex to males. The MSL complex binds to the X chromosome at hundreds of distinct loci, acetylates nucleosomes, and de-condenses the chromatin. Together with possibly many co-factors, the transcriptional up-regulation caused by MSL complex appears to counteract repressive factors to achieve an average effect of transcriptional doubling. Here, I have studied the initiation of MSL regulation on the X chromosome with a variety of approaches. In order to study early events, dosage compensation was induced in females with ectopic expression of msl2 from the tetracycline system. However, low background expression without activation prohibited further studies. To identify novel factors that affect dosage compensation, a reporter gene system based on variable eye size was evaluated. The system provided a dose-dependent phenotype, but could not report additional up-regulation by the MSL complex, and was thus unsuitable for the proposed mutational screen. The quantifiable lacZ gene was measured in a strict comparison of expression from an eye-specfic (GMR) or a constitutive (armadillo) promoter. At defined locations on the X chromsome, armadillo-lacZ acquired local compensation, but GMR-lacZ did not. Further modifications upstream of GMR-lacZ increased the response, and confirmed the importance of the promoter in attraction of dosage compensation. To corroborate this with the established importance of genic sequences in MSL attraction, a combinatorial model of attraction is proposed. The relative importance of early or constitutive expression was also tested, by providing GMR-lacZ with extra expression through the tetracycline system. A burst of embryonic expression, and constitutive expression, were both insufficient to increase dosage compensation of the transgene. Finally, the compensation of GMRmediated transgenes was confounded by ‘transvection’ effects of chromosome pairing. This effect may have wider implications on the study of compensation at individual genes

It's no riddle, choose the middle: the effect of number of crimes and topographical detail on police officer predictions of serial burglars' home locations.

This study examines the effect of the number of crimes and topographical detail on police officer predictions of serial burglars’ home locations. Officers are given 36 maps depicting three, five, or seven crime sites and topographical or no topographical details. They are asked to predict, by marking an X on the map, where they thought each burglar lived. After making their predictions on half of the maps, officers randomly receive either no training or training in one of two simple decision-making strategies. The accuracy of predictions at baseline and retest is measured as the distance between the predicted and actual home locations, and these accuracy scores are compared to a commonly used geographic profiling system. Results show that training significantly improved predictive accuracy, regardless of the number of crime locations or topographical detail presented. In addition, trained participants are as accurate as the geographic profiling system