RNA helicase DEAD-box-5 is involved in R-loop dynamics of preimplantation embryos

Area of Science:

• Molecular Biology
• Developmental Biology
• Epigenetics

Background:

• R-loops, DNA:RNA triplex structures, are critical for gene transcription and are dynamically regulated in mouse zygotes.
• Understanding R-loop regulation is crucial for deciphering early embryonic development and zygotic gene activation.
• Factors governing R-loop homeostasis in fertilized mouse eggs remain largely uninvestigated.

Purpose of the Study:

• To identify and investigate the functions of candidate factors regulating R-loop dynamics during zygotic gene activation in mouse embryos.
• To elucidate the role of specific proteins, such as DEAD-box-5 (DDX5) and histone deacetylase-2 (HDAC2), in R-loop metabolism.

Main Methods:

• Utilized publicly available next-generation sequencing data, including ribosome profiling and RNA polymerase II ChIP-seq, for candidate identification.
• Analyzed mass spectrometry data alongside sequencing datasets to pinpoint regulators of R-loop dynamics.
• Employed chemical inhibitors on in vitro fertilized mouse zygotes and quantified R-loop levels via immunofluorescence.

Main Results:

• DEAD-box-5 (DDX5) and histone deacetylase-2 (HDAC2) were identified as potential regulators of R-loop metabolism in oocytes, zygotes, and two-cell embryos.
• Inhibition of DDX5 activity significantly decreased R-loop accumulation in pronuclei, confirming its role in R-loop dynamics.
• Inhibition of HDAC2 activity did not yield a significant impact on R-loop levels in pronuclei.

Conclusions:

• Dynamic R-loop changes in mouse zygotes are likely orchestrated by RNA helicases, particularly DDX5, alongside transcriptional regulation.
• DDX5 plays a significant role in modulating R-loop dynamics during early embryonic development.
• This study provides crucial insights into the molecular mechanisms governing R-loop homeostasis in the crucial zygotic stage.