P-TEFb-mediated phosphorylation of hSpt5 C-terminal repeats is critical for processive transcription elongation.
Human DSIF, a heterodimer composed of hSpt4 and hSpt5, plays opposing roles in transcription elongation by RNA polymerase II (RNA Pol II). Here, we describe an evolutionarily conserved repetitive heptapeptide motif (consensus = G-S-R/Q-T-P) in the C-terminal region (CTR) of hSpt5, which, like the C-terminal domain (CTD) of RNA Pol II, is highly phosphorylated by P-TEFb. Thr-4 residues of the CTR repeats are functionally important phosphorylation sites. In vitro, Thr-4 phosphorylation is critical for the elongation activation activity of DSIF, but not to its elongation repression activity. In vivo, Thr-4 phosphorylation is critical for epidermal growth factor (EGF)-inducible transcription of c-fos and for efficient progression of RNA Pol II along the gene. We consider this phosphorylation to be a switch that converts DSIF from a repressor to an activator. We propose the "mini-CTD" hypothesis, in which phosphorylated CTR is thought to function in a manner analogous to phosphorylated CTD, serving as an additional code for active elongation complexes.
Yamada
Tomoko
T
Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, 4259 Nagatsuta, Yokohama 226-8501, Japan.
Yamaguchi
Yuki
Y
Inukai
Naoto
N
Okamoto
Sachiko
S
Mura
Takashi
T
Handa
Hiroshi
H
D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D001483:Base Sequence; D016762:Genes, fos; D006367:HeLa Cells; D006801:Humans; D066298:In Vitro Techniques; D008954:Models, Biological; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D042925:Positive Transcriptional Elongation Factor B / Q000235:genetics / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D012313:RNA / Q000235:genetics / Q000378:metabolism; D012319:RNA Polymerase II / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D020449:Repetitive Sequences, Amino Acid; D013912:Threonine / Q000737:chemistry; D014157:Transcription Factors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic; D035602:Transcriptional Elongation Factors / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*
D009687:Nuclear Proteins; D011994:Recombinant Proteins; C112224:SUPT5H protein, human; D014157:Transcription Factors; D035602:Transcriptional Elongation Factors; D013912:Threonine; D012313:RNA; D042925:Positive Transcriptional Elongation Factor B; D012319:RNA Polymerase II