Promoter-proximal pausing of RNA Polymerase II (PolII) is a widespread transcriptional regulatory mechanism in metazoans. DSIF and NELF cooperatively contribute to pausing by binding to PolII, and DSIF recruits NELF to the PolII elongation complex. To understand the molecular mechanism behind NELF recruitment by DSIF, I generated DSIF mutants based on available structural data and will test the ability of these mutants to recruit NELF in order to understand the biochemical interactions that drive pausing.