FMRP safeguards long mRNA expression by opposing repressive RNP states

FMRP loss in Drosophila oocytes shifts exceptionally long, FMRP-dependent mRNAs into Me31B-marked P-bodies, linking FMRP to protection from repressive RNP states.

• Why it matters: FMRP is often treated as a translational repressor, but its absence paradoxically reduces expression of very long neurodevelopmental transcripts, leaving the underlying mechanism unclear.
• What they did: In Drosophila oocytes, the study tested whether FMRP shields long mRNAs from Me31B/DDX6-driven repression, using Me31B P-body localization, transcriptome-wide co-occupancy mapping, and translation readouts after disrupting Me31B-dependent repression.
• The result: FMRP and Me31B show extensive co-occupancy, enriched on long coding sequences, and blocking Me31B repression preferentially enhances translation of FMRP targets in FMRP-deficient oocytes, implicating Rin/G3BP, Caprin, and Lig/UBAP2L as cofactors.

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