Proteomic analysis of interleukin enhancer binding factor 3 (Ilf3) and nuclear factor 90 (NF90) interactome.

Interleukin enhancer binding factor 3 (Ilf3) and Nuclear Factor 90 (NF90) are two ubiquitous proteins generated by alternative splicing from the ILF3 gene that provides each protein with a long and identical N-terminal domain of 701 amino acids and a specific C-terminal domain of 210 and 15 amino acids, respectively. They exhibit a high polymorphism due to their posttranscriptional and posttranslational modifications. Ilf3 and NF90 functions remain unclear although they have been described as RNA binding proteins but have been implicated in a large scale of cellular phenomena depending on the nature of their interacting partners, the composition of their protein complexes and their subcellular localization. In order to better understand the functions of Ilf3 and NF90, we have investigated their protein partners by an affinity chromatography approach. In this report, we have identified six partners of Ilf3 and NF90 that interact with their double-stranded RNA binding motifs: hnRNP A/B, hnRNP A2/B1, hnRNP A3, hnRNP D, hnRNP Q and PSF. These hnRNP are known to be implicated in mRNA stabilization, transport and/or translation regulation whereas PSF is a splicing factor. Furthermore, Ilf3, NF90 and most of their identified partners have been shown to be present in large complexes. Altogether, these data suggest an implication of Ilf3 and NF90 in mRNA metabolism. This work allows to establish a link between Ilf3 and NF90 functions, as RNA binding proteins, and their interacting partners implicated in these functions.