Transcription Start Site Mapping Using Super-low Input Carrier-CAGE.

Area of Science:

• Genomics
• Molecular Biology
• Epigenetics

Background:

• Cap analysis of gene expression (CAGE) identifies RNA polymerase II transcription start sites (TSSs).
• Accurate TSS detection is crucial for core promoter and active enhancer identification.
• Existing CAGE protocols require substantial RNA input, limiting their application.

Purpose of the Study:

• To describe a protocol for super-low input carrier-CAGE (SLIC-CAGE).
• To enable CAGE library preparation from nanogram amounts of total RNA.
• To facilitate TSS discovery and gene regulation studies with limited samples.

Main Methods:

• SLIC-CAGE utilizes an in vitro transcribed RNA carrier mix to minimize RNA loss.
• The carrier mimics DNA library fragment length, preventing bias.
• Homing endonucleases selectively degrade the carrier, protecting the target library.

Main Results:

• The protocol enables library preparation from nanogram-level total RNA (thousands of cells).
• The complete protocol, up to sequencing, is achievable within 6 days.
• Genome-wide, single-nucleotide resolution TSSs are obtained after sequencing.

Conclusions:

• SLIC-CAGE significantly reduces RNA input requirements for CAGE.
• The method supports core promoter and enhancer discovery.
• SLIC-CAGE provides valuable insights into gene regulation via 5'-centric expression profiling.