HP1γ binding pre-mRNA intronic repeats modulates RNA splicing decisions

Area of Science:

• Molecular Biology
• Epigenetics
• RNA Biology

Background:

• HP1 proteins are established heterochromatin markers involved in gene silencing.
• HP1γ (CBX3) is also an RNA-binding protein found on transcribed genes with RNA polymerase II, regulating co-transcriptional processes like alternative splicing.

Purpose of the Study:

• To investigate the role of HP1γ's RNA-binding activity in transcriptionally active chromatin.
• To identify RNAs associated with HP1γ and understand their functional implications.

Main Methods:

• RNA immunoprecipitation followed by sequencing (RIP-Seq) to capture and analyze RNAs bound by HP1γ.
• Bioinformatic analysis to identify RNA motifs and genomic elements associated with HP1γ.

Main Results:

• HP1γ specifically binds to hexameric RNA motifs and SINE family transposable elements.
• These SINE elements are predominantly found in introns, not exons.
• HP1γ-RNA association anchors unspliced pre-mRNA to chromatin via intronic regions.

Conclusions:

• HP1γ's RNA-binding function plays a role in co-transcriptional splicing by tethering pre-mRNA to chromatin.
• HP1γ limits the use of intronic cryptic splice sites, thereby influencing alternative splicing outcomes.
• This study reveals new insights into the interplay between chromatin structure and co-transcriptional RNA processing.