Dataset Information

RoX RNAs are required for increased expression of X-linked genes in Drosophila melanogaster males.

ABSTRACT: The male-specific lethal (MSL) ribonucleoprotein complex is necessary for equalization of X:A expression levels in Drosophila males, which have a single X chromosome. It binds selectively to the male X chromosome and directs acetylation of histone H4 at lysine 16 (H4Ac16), a modification linked to elevated transcription. roX1 and roX2 noncoding RNAs are essential but redundant components of this complex. Simultaneous removal of both roX RNAs reduces X localization of the MSL proteins and permits their ectopic binding to autosomal sites and the chromocenter. However, the MSL proteins still colocalize, and low levels of H4Ac16 are detected at ectopic sites of MSL binding and residual sites on the X chromosome of roX1- roX2- males. Microarray analysis was performed to reveal the effect of roX1 and roX2 elimination on X-linked and autosomal gene expression. Expression of the X chromosome is decreased by 26% in roX1- roX2- male larvae. Enhanced expression could not be detected at autosomal sites of MSL binding in roX1- roX2- males. These results implicate failure to compensate X-linked genes, rather than inappropriate upregulation of autosomal genes at ectopic sites of MSL binding, as the primary cause of male lethality upon loss of roX RNAs.

SUBMITTER: Deng X

PROVIDER: S-EPMC1698640 | biostudies-other | 2006 Dec

REPOSITORIES: biostudies-other

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roX RNAs are required for increased expression of X-linked genes in Drosophila melanogaster males.

Deng Xinxian X Meller Victoria H VH

Genetics 20061008 4

The male-specific lethal (MSL) ribonucleoprotein complex is necessary for equalization of X:A expression levels in Drosophila males, which have a single X chromosome. It binds selectively to the male X chromosome and directs acetylation of histone H4 at lysine 16 (H4Ac16), a modification linked to elevated transcription. roX1 and roX2 noncoding RNAs are essential but redundant components of this complex. Simultaneous removal of both roX RNAs reduces X localization of the MSL proteins and permits ...[more]

PMID: 17028315

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Project description:Drosophila males double transcription of their single X chromosome to equalize X-linked gene expression with females, which carry two X chromosomes. Increased transcription requires the Male-Specific Lethal (MSL) complex. One of the primary functions of the MSL complex is thought to be enrichment of H4Ac16 on the male X chromosome, a modification linked to elevated transcription. The roX1 and roX2 RNAs are essential but redundant components of the MSL complex. Simultaneous removal of both roX RNAs reduces MSL X-localization and leads to ectopic binding of these proteins at autosomal sites and to the chromocenter. Some H4Ac16 accumulates at these ectopic sites in roX1- roX2- males, suggesting the possibility of increased expression. The global effect of roX mutations on gene expression was measured by microarray analysis. We found that expression of the X chromosome was decreased by 26% in roX1- roX2- male larvae, supporting the involvement of roX RNAs in the up-regulation of X-linked genes. This finding is broadly comparable to reports of reduced X chromosome expression following msl2 RNAi knockdown in S2 cells. In spite of strong MSL binding and H4Ac16 accumulation at autosomal sites in roX1- roX2- males, enhanced gene expression could not be detected at these sites by microarray analysis or reverse northern blotting. Thus, failure to compensate X-linked genes, rather than inappropriate up-regulation of autosomal genes at ectopic sites of MSL binding, appears to cause male lethality upon loss of roX RNAs. Experiment Overall Design: Total RNA was prepared from groups of 50 third instar larvae by TRIzol (Invitrogen) extraction and purified using the RNeasy kit (Qiagen). Three independent RNA preparations for each genotype served as templates for probe synthesis. Affymetrix Drosophila Genome 2.0 chips were hybridized to these probes (Santa Clara, CA). The affymertrix Drosophila annotation of December 2004 was used to map genes to their cytological locations. Genes were filtered for present/absent calls by a PM-MM (Perfect match- Mismatch) comparison. Autosomal transcripts were normalized on a chip-by-chip basis to bring their median values to 100. The identical degree of adjustment was used to normalize X-linked transcripts. Changes in gene expression were determined by comparing the mean signal intensities of genes on arrays hybridized with roX1SMC17A roX2- probes to those hybridized with roX1+ roX2- probes.

Project description:We used microarrays to investigate the transcriptome of 6 days old male flies exposed to either 15 or 25 C development at either constant or fluctuating temperatures. Further, we investigated gene expression at benign (20C) and high (35C) temperatures With global climate change temperature means and variability are expected to increase. Thus, exposures to elevated temperatures are expected to become an increasing challenge for terrestrial ectotherm populations. While evolutionary adaptation seems to be constrained or proceed at an insufficient pace, many populations are expected to rely on phenotypic plasticity (thermal acclimation) for coping with the predicted changes. However, the effects of fluctuating temperature on the molecular mechanisms and the implications for heat tolerance are not well understood. To understand and predict consequences of climate change it is important to investigate how different components of the thermal environment, including fluctuating thermal conditions, contribute to changes in thermal acclimation. In this study we investigated the impact of mean and diurnal fluctuation of temperature on heat tolerance in Drosophila melanogaster and on the underlying molecular mechanisms in adult male flies. Flies from two constant and two ecologically relevant fluctuating temperature regimes were tested for their critical thermal maxima (CTmax) and associated global gene expression profiles at benign and thermally stressful conditions. Both temperature parameters contributed independently to the thermal acclimation, with regard to heat tolerance as well as the global gene expression profile. Although the independent transcriptional effects caused by fluctuations were relatively small, they are likely to be essential for our understanding of thermal adaptation. Thus, high temperature acclimation ability might not be measured correctly and might even be underestimated at constant temperatures. Our data suggests that the particular mechanisms affected by thermal fluctuations are related to phototransduction and environmental sensing. Thus genes and pathways involved in those processes are likely to be of major importance in a future warmer and more fluctuating climate.

Dataset Information

RoX RNAs are required for increased expression of X-linked genes in Drosophila melanogaster males.

Publications

roX RNAs are required for increased expression of X-linked genes in Drosophila melanogaster males.

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