Strand-specific, high-resolution mapping of modified RNA polymerase II

Area of Science:

• Molecular Biology
• Genetics
• Biochemistry

Background:

• The C-terminal domain (CTD) of RNA polymerase II (RNAPII) undergoes reversible phosphorylation.
• These modifications link transcription with RNA processing and surveillance.
• Understanding RNAPII CTD states is crucial for deciphering gene expression regulation.

Purpose of the Study:

• To map the location of RNAPII with specific CTD phosphorylations on RNA transcripts.
• To define RNAPII states using a machine learning approach.
• To investigate the relationship between RNAPII CTD modifications and different RNA classes.

Main Methods:

• Strand-specific, nucleotide-resolution mapping of RNAPII CTD phosphorylation.
• Machine learning-based approach (hidden Markov model) to define RNAPII states.
• Analysis of RNAPII distribution and associated factors across gene bodies.

Main Results:

• Enrichment of Ser5P and depletion of Tyr1P, Ser2P, Thr4P, and Ser7P near the transcription start site (TSS) of most genes.
• All modifications were depleted near the poly(A) site.
• Distinct RNAPII modification states identified: initiating, early elongating, and later elongating.
• Unstable non-coding RNAs (ncRNAs) showed distinct modification patterns and failed to transition to elongation states.

Conclusions:

• RNAPII CTD phosphorylation states are precisely regulated during transcription.
• These states correlate with distinct functional roles in transcription initiation, elongation, and RNA processing.
• Unstable ncRNAs exhibit unique RNAPII modification profiles, suggesting alternative regulatory pathways.