Activation of Young LINE-1 Elements by CRISPRa

Area of Science:

• Genomics
• Molecular Biology
• Epigenetics

Background:

• Long interspersed element-1 (LINE-1; L1s) are abundant mobile genetic elements in the human genome.
• L1s play roles in biological processes, and their dysregulation is linked to diseases and cancers.
• The functions of these repetitive elements remain largely uncharacterized.

Purpose of the Study:

• To investigate the functional roles of young Long interspersed element-1 (LINE-1; L1s) using CRISPR activation.
• To efficiently activate L1s in cultured human cells for functional studies.

Main Methods:

• Utilized the CRISPR activation (CRISPRa) system with catalytically dead Cas9 (dCas9).
• Applied CRISPRa in human L02 cells (a HeLa derivative) to induce L1 expression.
• Analyzed L1 subfamily expression, full-length status, and transcription factor occupancy (YY1).

Main Results:

• CRISPRa successfully activated L1s, with young subfamilies (L1HS, L1PA1, L1PA2) showing higher expression than older L1s.
• Highly transcribed L1s were more full-length and bound by the YY1 transcription factor.
• Activated L1s exhibited aberrant splicing into chimeric transcripts and acted as alternative promoters/enhancers for nearby genes.

Conclusions:

• CRISPR activation is an effective method for studying young L1s in cultured cells.
• Activated L1s can influence the expression of adjacent genes through various mechanisms.
• This approach facilitates research into the functional significance of L1 elements in biological contexts.