Transcription elongation factor SPT4 (hSPT4) (DRB sensitivity-inducing factor 14 kDa subunit) (DSIF p14) (DRB sensitivity-inducing factor small subunit) (DSIF small subunit)
1_MALET 6_ VPKDL 11_ RHLRA 16_ CLLCS 21_ LVKTI 26_ DQFEY 31_ DGCDN 36_ CDAYL 41_ QMKGN 46_ REMVY 51_ DCTSS 56_ SFDGI 61_ IAMMS 66_ PEDSW 71_ VSKWQ 76_ RVSNF 81_ KPGVY 86_ AVSVT 91_ GRLPQ 96_ GIVRE 101_ LKSRG 106_ VAYKS 111_RDTAI
1: Component of the DRB sensitivity-inducing factor complex (DSIF complex), which regulates mRNA processing and transcription elongation by RNA polymerase II (PubMed:10075709, PubMed:10199401, PubMed:10454543, PubMed:10912001, PubMed:11112772, PubMed:11553615, PubMed:12653964, PubMed:12718890, PubMed:15136722, PubMed:15380072, PubMed:9450929, PubMed:9857195). DSIF positively regulates mRNA capping by stimulating the mRNA guanylyltransferase activity of RNGTT/CAP1A (PubMed:15136722). DSIF also acts cooperatively with the negative elongation factor complex (NELF complex) to enhance transcriptional pausing at sites proximal to the promoter (PubMed:10199401, PubMed:10912001, PubMed:11112772). Transcriptional pausing may facilitate the assembly of an elongation competent RNA polymerase II complex (PubMed:10199401, PubMed:10912001, PubMed:11112772). DSIF and NELF promote pausing by inhibition of the transcription elongation factor TFIIS/S-II (PubMed:10199401, PubMed:10912001, PubMed:11112772). TFIIS/S-II binds to RNA polymerase II at transcription pause sites and stimulates the weak intrinsic nuclease activity of the enzyme (PubMed:16214896). 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 (PubMed:16214896). 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 (PubMed:11112772). 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 (PubMed:11112772)