4) nanos mRNA localization counteracts Vasa-mediated enhancement of Oskar mobility. While germ granule mRNA localization requires Vasa, this process opposes Vasa’s effect on Oskar condensates, providing an RNA-mediated negative feedback mechanism that regulates condensate properties.

3) mRNA localization to Oskar condensates requires Vasa and its interaction with Oskar. Although germ granules contain diverse proteins, Vasa and Oskar are necessary and sufficient for robust germ granule mRNA localization to the granules.

2) Vasa’s modulation of condensate properties requires direct protein-protein interaction. This activity requires specific binding interfaces between Vasa and Oskar, but is less dependent on Vasa helicase activity.

1) Vasa modulates the material properties of ribonucleoprotein condensates in fly oocytes and human cells. Recruitment of Vasa increases the mobility of the germ-granule nucleator Oskar, thereby preventing aggregation of granules.

This new function in regulating protein condensation extends beyond its established function as an RNA helicase. Specifically, Siran shows that:

She investigated the role of a conserved DEAD-box RNA helicase Vasa in condensation of germ granules in Drosophila. Her work reveals a previously unrecognized function of Vasa in regulating the material properties of Oskar ribonucleoprotein condensates through its direct interaction with Oskar.

4) Germ granule mRNAs are replete with GC-rich complementary sequences predicted to be competent of engaging in persistent intermolecular base pairing however in vivo these interactions are unrealized and restricted by RNA folding.

3) Engineered germ granule mRNAs with exposed GC-rich complementary sequences (CSs) within stem loops induce sustained base pairing in vitro and enhanced intermolecular interactions in vivo. But, the presence of these structures disrupts development, and GC-rich CSs exacerbate this phenotype.

We find that:
1) mRNAs remain structured within germ granules
2) mRNAs base pair intermolecularly without high sequence complementarity or significant melting of secondary structure. Base pairing is driven by scattered and discontinuous stretches of bases appearing on the surface of structured RNAs

Jeffery is presenting his work at the annual RNA society meeting in San Diego - visit his poster! #RNA25; #RNA2025

Jeffery is presenting his work at the annual RNA society meeting in San Diego - visit his poster! #RNA25; #RNA2025

We propose that the combined suppression of intermolecular base pairing and the increased RNA structural diversity may serve as a mechanism to preserve normal RNA function during stress, while also facilitating the reversible assembly of stress granules

c) However, these RNAs increase in structural diversity in a manner dependent on oxidative stress and the stress granule nucleating proteins G3BP1 and G3BP2.
d) In the absence of the main stress granule nucleating proteins G3BP1 and G3BP2, mRNAs remain dispersed in cells during oxidative stress

We show that:
a) Oxidative stress downregulates intermolecular base pairing of reporter mRNAs engineered to enhance detection of such interactions.
b) RNA regions within transcripts that enrich in stress granules remain structured during stress.