Transcript profiling in S2 cells and salivary glands.

Two chromosome-targeting and gene regulatory systems are present in Drosophila melanogaster. The male X-chromosome is targeted by the male-specific lethal complex believed to mediate the two-fold up-regulation of the X-linked genes. The highly heterochromatic 4th chromosome is specifically targeted by the Painting of Fourth (POF) protein which together with heterochromatin protein 1 (HP1) modulate the expression level of genes on the 4th chromosome. Here we report high-resolution mapping of POF and HP1 on the 4th chromosome using chromatin immunoprecipitation followed by tiling microarrays (ChIP-chip) in S2 cells and salivary glands. The enrichments are compared to transcript profiles of the two cell types used. POF specifically binds to genes with a strong preference for exons. The POF binding profile correlates to the binding profile of HP1 which in addition displays a typical “peak” in the promoter regions of bound genes. POF and HP1 binds to active genes and the binding correlates with levels of transcription and changes in binding levels are paralleled by a comparable change in transcription. Our results provide a high resolution description of the chromosome 4 specific gene regulatory system provided by the combinatorial effects of POF and HP1. Keywords: Transcript profiling Transcript profiling in S2 cells and salivary glands. Two biological replicates, one replicate per array.