Primary evidence checks for MEX-5 and MEX-6 (2026-09-20)

This note distinguishes the repository's abstract-only caches from article passages
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the first three papers were blocked or returned challenge/error pages; a complete
local copy was not obtained. These are short verified passages, not a replacement
full-text cache or a new provider report.

RNA binding: PMID:17264081

Pagano et al., JBC 2007,
DOI 10.1074/jbc.M700079200. The indexed Results describe purified tandem zinc-finger
fragments of BOTH MEX-5 and MEX-6 tested with the TNF-alpha 3′-UTR AU-rich element by
EMSA and fluorescence polarization:

Both methods reveal that MEX-5 and MEX-6 bind to TNF-ARE RNA.

MEX-5 binds poly-U as well as ARE substrates; reduced discrimination against other
U-rich sequences does not mean absence of ARE binding or absence of RNA sequence
preferences. MEX-6 is directly included despite the title naming only MEX-5.
The cache abstract defines the MEX-5 minimal site as six or more uridines within a
9–13-nucleotide window. No direct DNA-binding assay was established in this check.

Granule localization: PMID:12588843

Cuenca et al., Development 2003,
DOI 10.1242/dev.00284. Indexed Results state:

PIE-1:GFP, GFP:MEX-5 and GFP:MEX-6 all accumulated on granules in germline blastomeres.

This is GFP-fusion evidence for a particular developmental pool. Anterior enrichment
in the one-cell embryo and later association with germline granules are compatible.
Granule residence does not require being a structural scaffold; a role in granule
disassembly also does not exclude localization there.

Target-dependent translation: PMID:24131629

Oldenbroek et al., Development 2013,
DOI 10.1242/dev.096313. Indexed Results compare mom-2 and zif-1 regulation:

The contrary is true for mom-2, where POS-1 promotes translation in P2 and MEX-5/6 represses translation in EMS.

MEX-5 was tested in mom-2 3′-UTR binding assays; the in vivo repression experiments
use combined MEX-5/6 depletion. The pair-level genetic evidence and conserved PAINT
inference support MEX-6, without relabeling its individual repressor activity as a
purified-protein measurement. Promotion of zif-1 translation does not contradict
repression of mom-2. Reporter derepression is interpreted alongside RNA abundance
and genetic controls in the primary study.

RNA turnover and condensate disassembly: scope

PMID:18692039 describes CCR4-NOT-dependent recruitment of decapping components to
somatic P bodies. The MEX-6 Falcon report also discusses MEX-5/6-dependent LSM-1
recruitment and maternal RNA stability. This supports an RNA-turnover role; it does
not itself measure MEX-5 or MEX-6 catalysing poly(A) hydrolysis. The tail-shortening
IBA is retained as ancestral process participation, not direct enzymatic activity.

PMID:27594427 reconstituted prevention of PGL-3/RNA assembly and modeled spatial
segregation. PMID:40354522 directly tested dissolution of preassembled condensates
by full-length MEX-5. The latter uses a minimal tagged-protein/poly-rU system and
explicitly discusses differences from embryos, possible tag effects, kinases and
MEG proteins. Neither study directly tests purified MEX-6 in that assay.