PUMILIO, but not RBMX, binding is required for regulation of genomic stability by noncoding RNA <i>NORAD</i>.

Abstract

<i>NORAD</i> is a conserved long noncoding RNA (lncRNA) that is required for genome stability in mammals. <i>NORAD</i> acts as a negative regulator of PUMILIO (PUM) proteins in the cytoplasm, and we previously showed that loss of <i>NORAD</i> or PUM hyperactivity results in genome instability and premature aging in mice (Kopp et al., 2019). Recently, however, it was reported that <i>NORAD</i> regulates genome stability through an interaction with the RNA binding protein RBMX in the nucleus. Here, we addressed the contributions of <i>NORAD</i>:PUM and <i>NORAD</i>:RBMX interactions to genome maintenance by this lncRNA in human cells. Extensive RNA FISH and fractionation experiments established that <i>NORAD</i> localizes predominantly to the cytoplasm with or without DNA damage. Moreover, genetic rescue experiments demonstrated that PUM binding is required for maintenance of genomic stability by <i>NORAD</i> whereas binding of RBMX is dispensable for this function. These data provide an important foundation for further mechanistic dissection of the <i>NORAD</i>-PUMILIO axis in genome maintenance.