Distinctive sequence organization and functional programming of an Alu repeat promoter

Area of Science:

• Molecular Biology
• Genetics
• Biochemistry

Background:

• Human Alu family repeats are abundant repetitive elements in the genome.
• RNA polymerase III transcribes various small RNAs, including Alu repeats.

Purpose of the Study:

• To investigate the transcriptional properties of human Alu family repeats.
• To elucidate the promoter structure and function of an Alu repeat element.

Main Methods:

• In vitro transcription assays using HeLa cell extracts.
• Analysis of deletion and subclones of Alu repeat DNA.
• Topological studies of DNA templates (supercoiled, linear, nicked).

Main Results:

• Supercoiled DNA templates enhance transcription efficiency 3-5 fold.
• A contiguous DNA helix in the 5' flanking region (-30 to -85) is essential for initiation.
• The Alu repeat promoter is split, with a posterior element directing accurate initiation and an anterior element enhancing efficiency 10-20 fold.

Conclusions:

• The Alu repeat promoter has distinct directing and enhancing elements.
• The posterior element ensures accurate transcription initiation.
• The anterior element significantly boosts transcriptional efficiency.