| Research Abstract |
Transcription of protein coding genes is carried out by RNA polymerase II (RNAPII) and the general transcription factors (GTFs) TFIIB, TFIID, TFIIE, TFIIF, and TFIIH (Orphanides et al., 1996). The transcription process can be divided mechanistically into different steps. The binding of the GTFs to a promoter results in the recruitment of RNAPII and the initiation of transcription. This is followed by promoter clearance, elongation, and, finally, transcription termination. Spt4 forms a protein complex with Spt5 to regulate transcription elongation in vivo (Hartzog et al., 1996, 1998). Recently, our biochemical analysis revealed that human cells contain a counterpart to the Spt4/Spt5 complex.
We report that the chromatin-specific transcription elongation factor FACT functions in conjunction with the RNA polymerase II CTD kinase P-TEFb to alleviate transcription inhibition by DSIF (DRB sensitivity-inducing factor) and NELF (negative elongation factor). We find that the kinase activity of TFIIH is dispensable for this activity, demonstrating that TFIIH-mediated CTD phosphorylation is not involved in the regulation of FACT and DSIF/NELF activities. Thus, we propose a novel transcriptional regulatory network in which DSIF/NELF inhibition of transcription is prevented by P-TEFb in cooperation with FACT.This study uncovers a novel role for FACT in the regulation of transcription on naked DNA that is independent of its activities on chromatin templates. In addition, this study reveals functional differences between P-TEFb and TFIIH in the regulation of transcription.
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