RNA recognition motif 2 (RRM2) found in vertebrate insulin-like growth factor 2 mRNA-binding protein 1 (IGF2BP1)
This subgroup corresponds to the RRM2 of IGF2BP1 (IGF2 mRNA-binding protein 1 or IMP-1), also termed coding region determinant-binding protein (CRD-BP), or VICKZ family member 1, or zipcode-binding protein 1 (ZBP-1). IGF2BP1 is a multi-functional regulator of RNA metabolism that has been implicated in the control of aspects of localization, stability, and translation for many mRNAs. It is predominantly located in cytoplasm and was initially identified as a trans-acting factor that interacts with the zipcode in the 3'- untranslated region (UTR) of the beta-actin mRNA, which is important for its localization and translational regulation. It inhibits IGF-II mRNA translation through binding to the 5'-UTR of the transcript. IGF2BP1 also acts as human immunodeficiency virus type 1 (HIV-1) Gag-binding factor that interacts with HIV-1 Gag protein and blocks the formation of infectious HIV-1 particles. It promotes mRNA stabilization and functions as a coding region determinant (CRD)-binding protein that binds to the coding region of betaTrCP1 mRNA and prevents miR-183-mediated degradation of betaTrCP1 mRNA. It also promotes c-myc mRNA stability by associating with the CRD. It stabilizes CD44 mRNA via interaction with the 3'-UTR of the transcript. In addition, IGF2BP1 specifically interacts with both Hepatitis C virus (HCV) 5'-UTR and 3'-UTR, further recruiting eIF3 and enhancing HCV internal ribosome entry site (IRES)-mediated translation initiation via the 3'-UTR. IGF2BP1 contains four hnRNP K-homology (KH) domains, two RNA recognition motifs (RRMs), also termed RBDs (RNA binding domains) or RNPs (ribonucleoprotein domains), and a RGG RNA-binding domain. It also contains two putative nuclear export signals (NESs) and a putative nuclear localization signal (NLS).