Structure and function of the human transcription elongation factor DSIF

Area of Science:

• Molecular Biology
• Gene Regulation
• Biochemistry

Background:

• 5,6-Dichloro-1-beta-D-ribofuranosylbenzimidazole (DRB) inhibits RNA polymerase II (pol II) transcription elongation.
• A novel transcription elongation factor, DSIF (DRB sensitivity-inducing factor), was previously identified.
• DSIF, comprising 160- and 14-kDa subunits (homologs of Spt5 and Spt4), influences transcription sensitivity to DRB.

Purpose of the Study:

• To characterize the structure and function of the DSIF p160 subunit.
• To investigate the interaction of DSIF p160 with p14 and the pol II largest subunit.
• To elucidate the physiological role of DSIF in transcription regulation.

Main Methods:

• Ubiquitous nuclear protein expression analysis for p160.
• Co-immunoprecipitation to study complex formation between p160 and p14.
• Interaction studies between p160 and the pol II largest subunit.
• Site-directed mutagenesis to identify essential structural features and interaction domains.
• Dominant-negative mutant analysis to assess in vivo function.

Main Results:

• DSIF p160 is a ubiquitous nuclear protein forming a stable complex with p14.
• p160 directly interacts with the largest subunit of pol II.
• Mutation analysis identified key structural domains for p160 activity and interactions.
• A dominant-negative p160 mutant demonstrated DSIF's role in repressing transcription in vivo.

Conclusions:

• DSIF p160 is a crucial component of the DSIF complex, interacting with both p14 and pol II.
• DSIF plays a significant role in repressing transcription elongation in vivo.
• Understanding DSIF structure-function relationships provides insights into transcription regulation mechanisms.