Long non-coding RNA Neat1 and paraspeckle components are translational regulators in hypoxia

Internal ribosome entry sites (IRESs) drive translation initiation during
stress. In response to hypoxia, (lymph)angiogenic factors responsible for
tissue revascularization in ischemic diseases are induced by the
IRES-dependent mechanism. Here we searched for IRES trans-acting factors
(ITAFs) active in early hypoxia in mouse cardiomyocytes. Using knock-down
and proteomics approaches, we show a link between a stressed-induced
nuclear body, the paraspeckle, and IRES-dependent translation.
Furthermore, smiFISH experiments demonstrate the recruitment of
IRES-containing mRNA into paraspeckle during hypoxia. Our data reveal that
the long non-coding RNA Neat1, an essential paraspeckle component, is a
key translational regulator, active on IRESs of (lymph)angiogenic and
cardioprotective factor mRNAs. In addition, paraspeckle proteins p54nrb
and PSPC1 as well as nucleolin and Rps2, two p54nrb-interacting proteins
identified by mass spectrometry, are ITAFs for IRES subgroups. Paraspeckle
thus appears as a platform to recruit IRES-containing mRNAs and possibly
host IRESome assembly. Polysome PCR array shows that Neat1 isoforms
regulate IRES-dependent translation and, more widely, translation of mRNAs
involved in stress response.