PCNA directs type 2 RNase H activity on DNA replication and repair substrates

Area of Science:

• Molecular Biology
• Biochemistry
• Genetics

Background:

• Ribonuclease H2 (RNase H2) is crucial for degrading RNA/DNA hybrids and removing misincorporated ribonucleotides during DNA replication.
• Mutations in RNASEH2 are linked to Aicardi-Goutières syndrome, an autoimmune disorder potentially caused by DNA replication byproducts.

Purpose of the Study:

• To elucidate the structural and functional relationship between RNase H2 and PCNA.
• To understand how PCNA binding influences RNase H2 activity and localization during DNA replication.

Main Methods:

• Determined crystal structures of Archaeoglobus fulgidus RNase HII with PCNA and human PCNA with an RNASEH2B peptide.
• Investigated PCNA's effect on RNase HII activity and enzyme localization in vivo.

Main Results:

• Observed multiple binding modes of RNase HII to PCNA via its PIP-box motif and a flexible hinge.
• PCNA binding enhances RNase H2's ability to cleave misincorporated ribonucleotides and RNA primers.
• PCNA directs RNase H2 to nuclear replication foci, ensuring its dominance over RNase H1 during replication.

Conclusions:

• PCNA binding regulates RNase H2 activity and specificity during genome replication and repair.
• This regulation mechanism may prevent the generation of immunostimulatory nucleic acids, offering insights into Aicardi-Goutières syndrome pathogenesis.