Promoter-proximal pausing of RNA Polymerase II (PolII) is a widespread transcriptional regulatory mechanism. DSIF and NELF contribute to pausing by binding to PolII, and DSIF recruits NELF to PolII. To understand how DSIF recruits NELF, I generated DSIF mutants based on structural data and tested these mutants’ ability to bind NELF. The KOW2-3 domain of DSIF is important in NELF recruitment. This study provides mechanistic insight into regulation of promoter-proximal pausing by transcription factors.