Interact-with-SPT6 1 is a protein that was first characterized in yeast that was reported to be involved in postrecruitment of RNA-pol II mediated transcription. It is implicated in transcriptional elongation in yeast, human, and arabidopsis by directly interacting with the transcriptional elongation factor spt6. In Arabidopsis thaliana, IWS1 is involved in brassinosteroid regulated gene expression, and has been shown to interact with the transcription factor family BES1, which is activated by the BR receptor. ChIP experiments have shown that IWS1 binding is enriched at both the promoter and transcribed regions of target genes. These findings suggest that IWS1 is recruited by BES1 to the promoters of BR-responsive gene promoters under BR-induced conditions (PMID:20139304).