SUPT4H1
Function
Component of the DRB sensitivity-inducing factor complex (DSIF complex), which regulates mRNA processing and transcription elongation by RNA polymerase II. DSIF positively regulates mRNA capping by stimulating the mRNA guanylyltransferase activity of RNGTT/CAP1A. DSIF also acts cooperatively with the negative elongation factor complex (NELF complex) to enhance transcriptional pausing at sites proximal to the promoter. Transcriptional pausing may facilitate the assembly of an elongation competent RNA polymerase II complex. DSIF and NELF promote pausing by inhibition of the transcription elongation factor TFIIS/S-II. TFIIS/S-II binds to RNA polymerase II at transcription pause sites and stimulates the weak intrinsic nuclease activity of the enzyme. Cleavage of blocked transcripts by RNA polymerase II promotes the resumption of transcription from the new 3' terminus and may allow repeated attempts at transcription through natural pause sites. DSIF can also positively regulate transcriptional elongation and is required for the 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 and blocks premature release of HIV-1 transcripts at terminator sequences.
Post-translational modifications
Ubiquitinated by UBR5 when not assembled in the DSIF complex, leading to its degradation: UBR5 recognizes and binds a degron that is not accessible when SUPT4H1 is part of the DSIF complex.
Sequence Similarities
Belongs to the SPT4 family.
Tissue Specificity
Widely expressed.
Cellular localization
- Nucleus
Alternative names
SPT4H, SUPT4H, SUPT4H1, Transcription elongation factor SPT4, hSPT4, DRB sensitivity-inducing factor 14 kDa subunit, DRB sensitivity-inducing factor small subunit, DSIF p14, DSIF small subunit