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NOPS domain, including C-terminal coiled-coil region, in 54 kDa nuclear RNA- and DNA-binding protein (p54nrb) and similar proteins The family contains a DBHS domain (for Drosophila behavior, human splicing), which comprises two conserved RNA recognition motifs (RRMs), also termed RBDs (RNA binding domains) or RNPs (ribonucleoprotein domains), and a charged protein-protein interaction NOPS (NONA and PSP1) domain. This model corresponds to the NOPS domain, with a long helical C-terminal extension, found in p54nrb, also termed non-POU domain-containing octamer-binding protein (NONO), or 55 kDa nuclear protein (NMT55), or DNA-binding p52/p100 complex 52 kDa subunit. It is a multi-functional protein involved in numerous nuclear processes including transcriptional regulation, splicing, DNA unwinding, nuclear retention of hyperedited double-stranded RNA, viral RNA processing, control of cell proliferation, and circadian rhythm maintenance. p54nrb is ubiquitously expressed and highly conserved in vertebrates. It binds both single- and double-stranded RNA and DNA, and also possesses inherent carbonic anhydrase activity. p54nrb forms a heterodimer with paraspeckle component 1 (PSPC1 or PSP1), localizing to paraspeckles in an RNA-dependent manner. It also forms a heterodimer with polypyrimidine tract-binding protein-associated-splicing factor (PSF). The NOPS domain specifically binds to the second RNA recognition motif (RRM2) domain of the partner DBHS protein via a substantial interaction surface. Its highly conserved C-terminal residues are critical for functional DBHS dimerization while the highly conserved C-terminal helical extension, forming a right-handed antiparallel heterodimeric coiled-coil, is essential for paraspeckle localization to subnuclear bodies. |
Jiyao W et al.(2023). "The conserved domain database in 2023.",