Poster abstracts
Poster number 150 submitted by Belal Chowdhury
FAM120A couples selective mRNA recognition to translation initiation and autoregulates its own translation through a 5′-UTR uORF-m6A module
Belal Chowdhury (Department of Biochemistry & Biophysics, University of Rochester Medical Center), Peng Yao (1. Aab Cardiovascular Research Institute, 2. Department of Biochemistry & Biophysics, University of Rochester Medical Center)
Abstract:
FAM120A (family with sequence similarity 120 member A) is an oxidative-stress-associated RNA-binding protein whose mRNA targets, engagement with the translation-initiation apparatus, and autoregulation remain poorly characterized. RIP-seq in HEK293T cells identified high-confidence FAM120A-bound mRNAs, including IGF2BP1/2/3, PP2A-complex subunits, and translation-initiation/stress-sensing factors (EIF4A1, EIF5A, EIF2AK1/HRI, EIF2AK2/PKR), nominating FAM120A as a post-transcriptional hub for translational reprogramming.
To determine how FAM120A engages this machinery, we combined TurboID proximity-labeling mass spectrometry (MS) with immunoprecipitation (IP)-MS with and without benzonase treatment, distinguishing direct protein contacts from RNA-bridged ones. TurboID placed FAM120A among eIF2, eIF3, and eIF4 family members. The entire eIF3 octamer, central to 43S complex assembly and ribosome scanning, remained bound to FAM120A after RNA digestion, indicating a stable, protein-level association with the ribosome-recruitment machinery. By contrast, the cap-binding complex (eIF4E/4E-T) and eIF2 ternary complex required intact RNA to co-purify, and elongation factors dissociated entirely, pointing to a role for FAM120A specifically at initiation.
FAM120A also autoregulates its own translation via a conserved 5′-UTR upstream open reading frame (uORF) bearing an m6A mark immediately upstream of its start codon. Dual-luciferase assays showed that disrupting the uORF start codon relieved repression of the main ORF, and removing the m6A mark further derepressed translation, indicating that the uORF and m6A act together to control FAM120A translation.
Together, these findings position FAM120A as a translational regulator that engages ribosome recruitment via eIF3 and is itself governed by uORF-m6A autoregulation. Studies are underway to define this stress-responsive circuit and FAM120A's biological function using a knockout mouse model.
Keywords: m6A modification, 5-UTR upstream open reading frame, Translation initiation