Delta sleep-inducing factor (DSIF) is a protein complex that plays a role in the regulation of gene expression, particularly during the process of transcription, which is the first step in the synthesis of RNA from DNA. DSIF is also known as DRB sensitivity-inducing factor (DSIF) or 5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole (DRB) sensitivity-inducing factor.
DSIF is composed of two subunits: SPT4 (Suppressor of Ty 4) and SPT5 (Suppressor of Ty 5). It was initially discovered in yeast, where it was found to be involved in controlling the elongation of RNA polymerase II (RNAPII) during transcription. RNAPII is the enzyme responsible for transcribing protein-coding genes into messenger RNA (mRNA).
DSIF acts as a regulator of transcription elongation by controlling the rate at which RNAPII moves along the DNA template strand. It can either promote or inhibit transcription elongation, depending on its interaction with other factors. When DSIF is associated with other proteins like NELF (Negative Elongation Factor), it can cause pausing of RNAPII and inhibit transcription elongation. However, when DSIF interacts with positive elongation factors, it can promote efficient transcription.
DSIF's role in transcription regulation is critical for proper gene expression, and its activity can be influenced by various signaling pathways and factors within the cell. Dysregulation of DSIF function can have significant consequences on gene expression and cellular processes, and it has been studied in the context of various diseases and conditions, including cancer and HIV infection.