P{w^RW} is designed for use in an enhancer-blocking assay, which can be used to define and characterize chromatin domain boundary elements. P{w^RW} contains the w transcription unit plus approximately 1860bp of w upstream sequence (which contains eye and testis enhancers). A polylinker sequence (ClaI-ScaII of pKS, contains the unique restriction sites XbaI and NotI) has been inserted at position -315 relative to the transcription start site. A 500bp scs' element has been inserted downstream of the w coding region to reduce position effects from the 3' side. Sequence to be tested for enhancer-blocking activity can be inserted into the polylinker between the promoter and upstream enhancers, to analyse the effect on pigment expression in the eye and testis compared to the level seen in flies carrying the original P{w^RW} element without the inserted sequence.

Construct: 0.5kb of scs' sequences.