DSIF

DSIF ( D RB S ensitivity I nducing F actor) is a factor that can either negatively or positively affect transcription by RNA polymerase II (Pol II). In one case of negative regulation, it can interact with NELF to promote the stalling of Pol II at some genes. This stalling is released by P-TEFb. In humans, DSIF is composed of hSPT4 and hSTP5 (SPT4 and SPT5 are homologues in yeast).