Biopolym. Cell. 2019; 35(3):176-177.
Chronicle and Information
Nuclear lipid Islets as integrators of Polymerase II transcription and pre-mRNA processing
1Sztacho M., 1, 2, 3Hozak P.
  1. Institute of Molecular Genetics ASCR v.v.i., Department of Biology of the Cell Nucleus
    Vídeňská 1083, 142 20, Prague 4, Czech Republic
  2. Microscopy Centre, Institute of Molecular Genetics ASCR v.v.i.
    Vídeňská 1083, 142 20, Prague 4, Czech Republic
  3. Institute of Molecular Genetics ASCR v.v.i., Division BIOCEV, Laboratory of Epigenetics of the Cell Nucleus
    Průmyslová 595, 252 50, Vestec, Czech Republic


The eukaryotic nuclear environment possess a dynamic highly organized architecture. Processes such as gene expression, DNA repair or RNA processing occur often in membrane-less compartments. These structures constitute of e.g. nucleic acids, proteins, lipid multimolecular condensates. Our laboratory recently discovered nanoscale globular (~100 nm) Nuclear Lipid Islets (NLIs) structures containing PI(4,5)P2 (PIP2), which are involved in efficient RNAPII transcription [1]. We aim to describe the possible function of PIP2-containing NLIs in integrating RNAPII transcription and pre-mRNA splicing at their surface. Methods: To decipher whether PIP2-containing NLIs surface recruit a regulatory proteins abovementioned processes, we employed a comparative quantitative mass spectrometry (MS) analysis of PIP2 nuclear fraction combined with super-resolution microscopy visualization of candidate proteins. Results: Our quantitative MS approach identified more than 300 putative NLIs proteins, which represents 35% of nuclear PIP2 – associated proteins. Moreover, 50 % of those proteins are connected to gene expression and more that 30 % to RNA processing. Super-resolution microscopy showed that candidate proteins form foci in nucleoplasm and associate with sub-population of NLIs. In contrary, proteins predicted by MS as NLIs-nonassociated showed random distribution in respect to nucleoplasmic PIP2 foci. Conclusions: It is known that RNA splicing occurs co-transcriptionally. We show that sub-population of NLIs interact with regulators of both RNAPII transcription and pre-mRNA splicing [2]. We hypothesis that the surface of NLIs facilitate spatiotemporal regulation of these processes. Funding: This study was supported by the Czech Academy of Sciences (JSPS-18-18); Grant Agency of the Czech Republic (16-03346S, 17-09103S, 15-08738S); Technology Agency of the Czech Republic (TE01020118); IMG ASCR, v. v. i.(RVO: 68378050); European Regional Development Fund (CZ.02.1.01/0.0/0.0/16_013/0001775). Microscopy Centre - IMG AS CR the Czech-BioImaging project (LM2015062 funded by MEYS CR). References: 1. Sobol, M., et al., Nuclear phosphatidylinositol 4,5-bisphosphate islets contribute to efficient RNA polymerase II-dependent transcription. J Cell Sci, 2018. 131(8). 2. Sztacho, M., et al., Nuclear phosphoinositides and phase separation: Important players in nuclear compartmentalization. Adv Biol Regul, 2018.