Mammalian mRNA can be post-transcriptionally modified by site-specific adenosine or citidine deaminases in a process known as mRNA editing. Editing by deamination is catalyzed by enzymes known as CDARs (cytidine deaminases active on RNA) and results in a change from cytidine to uridine. Apobec1 edits the ApoB mRNA by deaminating nucleotide C⁶⁶⁶⁶. This results in a codon change from Glu to stop, causing the expression of a protein variant of 48 instead of 100 kDa. Apobec1 is regulated by protein factors that are present in the apoB mRNA editing complex. One essential factor is ACF1 (Apobec1 complementation factor). Another, possibly inhibitory, component of the ApoB RNA editing complex is hnRNPQ protein, which interestingly shares several of the domains presents ACF1. HnRNPQ binds to Apobec1, ACF1 and ApoB mRNA and consists of a N-terminal "acidic domain" (AcD), of yet unknown function, three RNA recognition motifs, and an Arg/Gly-rich region. Here, we describe the molecular modeling of the AcD of hnRNPQ by using the bacterial protein Barstar as a molde. Furthermore, we demonstrated by in vitro pull down assays with recombinant fusion proteins that 6xHis-hnRNPQ-AcD is able to interact with GST-Apobec1.  Finally, we performed in silico phosphorylation of hnRNPQ and molecular dynamics studies of the apo- and phospho-forms of the protein. The results of the latter studies were confirmed and detailed by in vitro phosphorylation of 6xHis-hnRNPQ-AcD, mass spectrometry and circular dichroism spectroscopy analyses. In summary, our data suggest that hnRNPQ interacts via its AcD with Apobec1 and that this interaction could be subject to regulation by phosphorylation of this domain, which results in conformational changes in this protein domain.