Two distinct nuclear stress bodies containing different sets of RNA-binding proteins are formed with HSATIII architectural noncoding RNAs upon thermal stress exposure.

Nuclear stress bodies (nSBs) are thermal stress-inducible membrane-less nuclear bodies that are formed on highly repetitive satellite III architectural noncoding RNAs (HSATIII arcRNAs). Upon thermal stress exposure, HSATIII expression is induced to sequestrate specific sets of RNA-binding proteins and form nSBs. The major population of nSBs contain SAFB as a marker, whereas the minor population are SAFB-negative. Here, we found that HNRNPM, which was previously reported to localize in nuclear foci adjacent to SAFB-positive foci upon thermal stress, localizes in a minor population of HSATIII-dependent nSBs. Hence, we used the terms nSB-S and nSB-M to distinguish the SAFB foci and HNRNPM foci, respectively. Analysis of the components of the nSBs revealed that each set contains distinct RNA-binding proteins, including SLTM and NCO5A in nSB-Ss and HNRNPA1 and HNRNPH1 in nSB-Ms. Overall, our findings indicate that two sets of nSBs containing HSATIII arcRNAs and distinct sets of RNA-binding proteins are formed upon thermal stress exposure.