Regulation of nuclear architecture of neuronal cells by nuclear matrix protein SP120

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Several neuron-specific genes placed in the AT-rich genomic environment are regulated by DNA topoisomerase (topo) IIβ. We have identified hnRNP U/SAF-A/SP120 as a protein associated with topo IIβ in differentiating cerebellar neurons. SP120 is a multifunctional nuclear protein that directly binds to DNA and RNA. SP120 specifically and cooperatively binds AT-rich matrix attachment regions (MAR). It was the reported that the N-terminal domain termed SAF-box was required for DNA binding and the C-terminal domain called RGG-box was essential for the interaction with RNA. We showed that a C-terminal domain enriched with Arg-Gly (RG domain) encompassing the RGG-box was important for the MAR-specific binding activity.