Systematic Identification of Germ Granule Proteins Reveals Specialized Roles in RNAi and Small RNA Inheritance

Area of Science:

• * Molecular Biology
• * Genetics
• * Developmental Biology

Background:

• * Biomolecular condensates like germ granules are crucial for RNA interference (RNAi) pathways, impacting fertility and genome regulation.
• * The precise protein makeup and functions of these condensates are not fully understood.
• * Understanding germ granule composition is key to deciphering small RNA pathway regulation.

Purpose of the Study:

• * To systematically identify and characterize proteins within C. elegans germ granules.
• * To elucidate the functional roles of newly identified proteins in fertility, germline maintenance, and small RNA pathways.
• * To investigate the evolutionary relationship and functional significance of key protein interactors.

Main Methods:

• * TurboID proximity labeling of the germ granule protein SIMR-1.
• * Integration of mass spectrometry, genetic screening, and CRISPR-based gene tagging.
• * Small RNA sequencing and comparative genomics.

Main Results:

• * Identification of novel germ granule proteins influencing fertility, germline immortality, exogenous RNAi, and transgenerational inheritance.
• * Discovery of PINT-1, a disordered protein interacting with PIWI Argonaute PRG-1, essential for secondary siRNA biogenesis and germline development.
• * Small RNA sequencing revealed specific defects in siRNA and miRNA biogenesis linked to different protein factors.
• * Comparative genomics showed PINT-1 co-evolved with PRG-1 in nematodes.

Conclusions:

• * The study expands the known proteome of germ granules, revealing diverse functional contributions of condensate components.
• * Distinct proteins within germ granules play specialized roles in regulating various small RNA pathways.
• * PINT-1 represents an evolutionarily co-adapted interactor critical for siRNA biogenesis and germline function.