RNA recognition motif 1 (RRM1) found in RNA-binding protein Musashi homolog 1 (Musashi-1) and similar proteins
This subgroup corresponds to the RRM1 of Musashi-1. The mammalian MSI1 gene encoding Musashi-1 (also termed Msi1) is a neural RNA-binding protein putatively expressed in central nervous system (CNS) stem cells and neural progenitor cells and associated with asymmetric divisions in neural progenitor cells. Musashi-1 is evolutionarily conserved from invertebrates to vertebrates. It is a homolog of Drosophila Musashi and Xenopus laevis nervous system-specific RNP protein-1 (Nrp-1). Musashi-1 has been implicated in the maintenance of the stem-cell state, differentiation, and tumorigenesis. It translationally regulates the expression of a mammalian numb gene by binding to the 3'-untranslated region of mRNA of Numb, encoding a membrane-associated inhibitor of Notch signaling, and further influences neural development. Moreover, it represses translation by interacting with the poly(A)-binding protein and competes for binding of the eukaryotic initiation factor-4G (eIF-4G). Musashi-1 contains two conserved N-terminal tandem RNA recognition motifs (RRMs), also termed RBDs (RNA binding domains) or RNPs (ribonucleoprotein domains), along with other domains of unknown function.