IVNS1ABP (influenza virus NS1A binding protein) is a multifunctional host protein that plays critical roles in both viral and cellular RNA processing. The protein facilitates influenza A virus replication by promoting alternative splicing of viral M1 mRNA to generate M2 mRNA through interactions with HNRNPK 1. IVNS1ABP binds to M mRNA downstream of the M2 5' splice site, partially overlapping the U1 snRNP binding site, and works cooperatively with hnRNP K to regulate splicing efficiency 1. Additionally, IVNS1ABP promotes nuclear export of viral M mRNAs by competing with viral NS1 protein for binding to the mRNA export receptor NXF1, allowing recruitment of export machinery despite NS1-mediated nuclear retention of cellular mRNAs 2. Beyond viral functions, IVNS1ABP expression is regulated by miR-145-5p and miR-548an, with dysregulation linked to gastric cancer progression and influenza infection responses 34. The protein also functions in cellular processes including proteasome-mediated protein degradation and transcriptional regulation. Disease associations include primary immunodeficiency (Immunodeficiency 70) identified through whole-genome sequencing studies 5, highlighting its importance in immune system function.