DRB sensitivity-inducing factor complex (DSIF complex, DSIF)

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Function

regulates mRNA processing & transcription elongation by RNA polymerase 2
regulates mRNA capping by stimulating mRNA guanylyltransferase activity of RNGTT.
acts cooperatively with NELF complex to enhance transcriptional pausing at sites proximal to the promoter
transcriptional pausing may facilitate assembly of elongation competent RNA polymerase 2
DSIF & NELF inhibit transcription elongation factor TFIIS
TFIIS binds to RNA polymerase 2 at transcription pause sites & stimulates its weak intrinsic nuclease activity
cleavage of blocked transcripts by RNA polymerase 2 promotes resumption of transcription from the new 3' terminus & may allow repeated attempts at transcription through natural pause sites
DSIF can also upregulate transcriptional elongation
required for efficient activation of transcriptional elongation by the HIV-1 nuclear transcriptional activator, Tat
DSIF acts to suppress transcriptional pausing in transcripts derived from the HIV-1 LTR & blocks premature release of HIV-1 transcripts at terminator sequences
DSIF interacts with P-TEFb complex
DSIF interacts with RNA polymerase 2, & this interaction is diminished by phosphorylation of the C-terminal domain (CTD) of POLR2A by P-TEFb
DSIF also interacts with the NELF complex; interaction occurs following prior binding of DSIF to RNA polymerase 2
DSIF also interacts with HRMT1L2/PRMT1, HTATSF1/TATSF1, RNGTT/CAP1A, SKB1/PRMT5, SUPT6H, & can interact with PIN1