To identify novel ITSN1 and ITSN2 partners among RNA-binding proteins (RBPs) involved in the regulation of mRNA processing. Methods. The interactions were revealed using GST pull-down and immunoprecipitation assays whereas bioinformatics analysis was used to identify other RBPs that could interact with proteins ITSN1 and ITSN2. Results. It was shown that ITSN1 and ITSN2 SH3 domains interacted with nuclear RBPs SAM68, WBP11, and LARP6 in vitro. Next, it was found that ITSN1 and ITSN2 co-precipitated with SAM68 and LARP6 from 293 cells lysates. Finally, the bioinformatics analysis identified more than 500 nuclear RBPs that contain several SH3 domain-interacting proline motifs and could bind ITSN1/2. Conclusions. ITSN1 and ITSN2 SH3 domains bind nuclear RBPs SAM68, LARP6, and WBP11 in vitro, form complexes with SAM68 and LARP6 in 293 cells, and potentially could interact with other nuclear RBPs containing SH3 domain-interacting motifs.
Introduction. SAM68 (Src associated in mitosis of 68 kDa, KHDRBS1) is an RNA-binding protein involved in the regulation of transcription, alternative splicing, RNA maturation, and signalling processes in a cell [1]. SAM68 central KH domain mediates RNA binding, whereas proline-rich regions, tyrosine motifs, and RG repeats located in the non-structured N-and C-terminal regions provide the binding to protein partners. Multiple studies reveal the protooncogenic properties of SAM68, while its overexpression is observed in glioblastoma, breast, prostate, colorectal, cervical and other types of cancer, whereas SAM68 depletion inhibits cells proliferation [2]. SAM68 interacts with various splicing factors and spliceosome-associated proteins and binds A/U rich sequences in RNA. This protein is involved in the alternative splicing of va rious mR
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