Identification of a Heat-inducible Novel Nuclear Body Containing the Long Noncoding RNA MALAT1

The heat-shock response is critical for the survival of all organisms. Metastasis-associated long adenocarcinoma transcript 1 (MALAT1) is a long noncoding RNA localized in nuclear speckles, but its physiological role remains elusive. Here, we show that heat shock induces translocation of MALAT1 to a distinct nuclear body named the heat shock-inducible noncoding RNA-containing nuclear (HiNoCo) body in mammalian cells. MALAT1-knockout A549 cells showed reduced proliferation after heat shock. The HiNoCo body, which is formed adjacent to nuclear speckles, is distinct from any other known nuclear bodies, including the nuclear stress body, Cajal body, germs, paraspeckles, nucleoli and promyelocytic leukemia body. The formation of HiNoCo body is reversible and independent of heat shock factor 1, the master transcription regulator of the heat-shock response. Our results suggest the HiNoCo body participates in heat shock factor 1-independent heat-shock responses in mammalian cells.