Interaction, mobility, and phosphorylation of human orthologues of WD repeat-containing components of the yeast SSU processome t-UTP sub-complex

Biochem Cell Biol. 2013 Dec;91(6):466-75. doi: 10.1139/bcb-2013-0062. Epub 2013 Jul 25.

Abstract

We previously proposed a dynamic scaffold model for inner nuclear structure formation. In this model, structures in inter-chromatin regions are maintained through dynamic interaction of protein complex modules, and WD repeat- and disordered region-rich proteins and others act as scaffolds for these protein complexes. In this study, three WD-repeat proteins, i.e., CIRH1A, UTP15, and WDR43, were found in the nuclear matrix fraction and speculated to be present in the human t-UTP sub-complex of SSU processomes. The results obtained as to their subnuclear localization, binding with each other, mobilities, and phosphorylation were: (i) the majority of these proteins fused with GFP are localized to the fibrillar center region in nucleoli. (ii) these 3 proteins bind directly with each other in vitro. (iii) the movement of these proteins is very slow in living cells and independent of rDNA transcription. (iv) His-CIRH1A is phosphorylated at Thr(131) by a mitotic Xenopus egg extract, and binding with GST-UTP15 and GST-WDR43 is suppressed. These findings and others suggest that these 3 WD proteins found in the matrix fraction bind directly with each other, bind tightly to fibrillar center regions, and comprise a part of the nucleolar structure. These results are also consistent with our dynamic scaffold model.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Carrier Proteins / genetics
  • Carrier Proteins / metabolism*
  • Cell Nucleolus / genetics
  • Cell Nucleolus / metabolism*
  • Cell Nucleolus / ultrastructure
  • Escherichia coli / genetics
  • Escherichia coli / metabolism
  • Fungal Proteins / genetics
  • Fungal Proteins / metabolism
  • Gene Expression Regulation
  • Genes, Reporter
  • Green Fluorescent Proteins / genetics
  • Green Fluorescent Proteins / metabolism
  • HeLa Cells
  • Humans
  • Nuclear Matrix / genetics
  • Nuclear Matrix / metabolism*
  • Nuclear Matrix / ultrastructure
  • Nuclear Proteins / genetics
  • Nuclear Proteins / metabolism*
  • Phosphorylation
  • Protein Binding
  • Protein Interaction Domains and Motifs
  • Protein Transport
  • Ribonucleoproteins / genetics
  • Ribonucleoproteins / metabolism*
  • Signal Transduction
  • Xenopus laevis / metabolism

Substances

  • Carrier Proteins
  • Fungal Proteins
  • Nuclear Proteins
  • Ribonucleoproteins
  • UTP4 protein, human
  • Green Fluorescent Proteins