FAM120A

FAM120A (Ossa/C9orf10) is a multifunctional RNA-binding scaffold protein that couples RNA metabolism to cell survival, growth, and metastatic signaling (PMID:19015244, PMID:31289130). In its scaffolding role, FAM120A is activated upon oxidative stress (UV) by associating with Src family kinases, becoming tyrosine-phosphorylated, and then recruiting the p85 subunit of PI3-kinase to assemble a Src/PI3K platform that drives Akt antiapoptotic signaling (PMID:19015244); it performs the analogous function downstream of the IL13Rα2 receptor, bridging PI3K recruitment and Src-mediated activation to engage FAK and the PI3K/AKT/mTOR axis and promote colon cancer invasion and metastasis (PMID:25896327). Consistent with this pro-metastatic activity, elevated FAM120A phosphorylation activates Src family kinases and supports anchorage-independent growth and bone metastasis (PMID:38339971). As an RNA-binding protein, FAM120A interacts with Ago2 and binds homopolymeric poly(G) tracts in thousands of 3'-UTRs, shielding those transcripts from Ago2/miRNA-mediated degradation (PMID:31289130), and it stabilizes specific transcripts including SLC7A11 mRNA to suppress ferroptosis and confer cisplatin resistance (PMID:38565940). FAM120A also acts as a co-activator that bridges SREBP1 at active promoters to an SRSF1/U1-70K splicing machinery downstream of mTORC1-SRPK2 signaling, coupling transcription and splicing of lipogenic genes to fatty acid synthesis and proliferation (PMID:37595559). Through its intrinsically disordered RNA-binding domain it partitions into stress granules and stabilizes the lncRNA MALAT1 to promote chemoresistance (PMID:41328536).

1. 2008 Medium

   Established FAM120A as a stress-activated signaling scaffold, answering how oxidative stress is coupled to survival signaling.

   Evidence Co-IP, tyrosine phosphorylation assays, and survival readouts in gastric carcinoma cells

   PMID:19015244

   Open questions at the time

   • Phosphosite identity on FAM120A not mapped
   • direct vs indirect SFK association not resolved
   • mechanism of stress sensing unknown
2. 2008 Low

   Initial evidence that FAM120A is an RNA-binding protein, linking it to mRNA-protein particles and secretion.

   Evidence RNA-binding assays and IGF-II secretion measurement in cancer cells; Co-IP with Puralpha and immunohistochemistry in mouse brain

   PMID:18413649 PMID:19015244

   Open questions at the time

   • RNA-binding specificity not characterized at this stage
   • Puralpha interaction lacks functional validation
   • neuronal role undefined
3. 2015 High

   Defined FAM120A as the scaffold that transmits IL13Rα2 receptor signaling to PI3K/FAK/AKT, explaining its pro-metastatic function.

   Evidence Reciprocal Co-IP, siRNA/shRNA silencing, in vitro invasion assays, and in vivo liver colonization in nude mice

   PMID:25896327

   Open questions at the time

   • Structural basis of the IL13Rα2-FAM120A-PI3K assembly not resolved
   • whether RNA-binding contributes to this scaffolding role unknown
4. 2019 High

   Revealed a post-transcriptional function: FAM120A sequesters Ago2 on poly(G) 3'-UTRs to protect transcripts from miRNA silencing.

   Evidence Ago2-IP/MS, transcriptome-wide iCLIP, and 3'-UTR reporter assays in mouse embryonic stem cells

   PMID:31289130

   Open questions at the time

   • How FAM120A blocks Ago2 catalytic activity mechanistically unknown
   • physiological targets in disease contexts not defined
5. 2023 High

   Connected FAM120A to growth signaling by showing it bridges transcription and splicing of lipogenic genes downstream of mTORC1-SRPK2.

   Evidence Co-IP, ChIP, in vitro SRPK2 kinase assays, knockdown transcriptomics/splicing analysis, and proliferation assays

   PMID:37595559

   Open questions at the time

   • Generality beyond lipogenic genes not established
   • structural detail of the Pol II-FAM120A-spliceosome bridge unknown
6. 2024 Medium

   Linked FAM120A RNA-stabilizing activity to ferroptosis resistance and chemosensitivity via SLC7A11 mRNA, and placed it under m6A control.

   Evidence RIP, mRNA stability and m6A assays, knockdown with ferroptosis/cisplatin readouts, and xenografts in gastric cancer

   PMID:38565940

   Open questions at the time

   • Direct binding site on SLC7A11 mRNA not mapped
   • whether the poly(G)/Ago2 mechanism underlies this stabilization untested
7. 2024 Medium

   Reinforced the phospho-FAM120A/Src axis as a driver of metastasis in lung adenocarcinoma.

   Evidence Phosphorylation assays, shRNA knockdown, anchorage-independent growth, and intracardiac metastasis model in nude mice

   PMID:38339971

   Open questions at the time

   • Phosphorylation sites driving the effect not identified
   • upstream kinase/trigger in this context unclear
8. 2026 Medium

   Identified the disordered RNA-binding domain as the determinant of stress-granule localization and showed MALAT1 stabilization mediates chemoresistance.

   Evidence eCLIP-seq, RIP-qPCR, domain mutagenesis, stress granule imaging, and MALAT1 overexpression rescue in cisplatin-resistant NSCLC

   PMID:41328536

   Open questions at the time

   • Mechanism by which MALAT1 confers resistance not detailed
   • relationship between SG partitioning and RNA stabilization unresolved

• How FAM120A's distinct scaffolding (PI3K/Src) and RNA-binding (Ago2, mRNA stabilization, splicing) activities are coordinated within a single protein remains unresolved.
• No structural model integrating signaling and RNA-binding domains
• domain dependencies across functions not systematically dissected
• regulatory switch between activities unknown