Interaction, mobility, and phosphorylation of human orthologues of WD repeat-containing components of the yeast SSU processome t-UTP sub-complex.
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.
a Graduate School of Science and Technology, Niigata University, Igarashi-2, Nishi-ku, Niigata 950-2181, Japan.
Manae
M
Sato
Nanase
N
Araki
Masahiro
M
Kumeta
Kunio
K
Takeyasu
Yusuke
Y
Taguchi
Takahiro
T
Asai
Kazuhiro
K
Furukawa
Tsuneyoshi
T
Horigome
D000818:Animals; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D002466:Cell Nucleolus / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism; D005786:Gene Expression Regulation; D017930:Genes, Reporter; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D015530:Nuclear Matrix / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D011485:Protein Binding; D054730:Protein Interaction Domains and Motifs; D021381:Protein Transport; D012261:Ribonucleoproteins / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D014982:Xenopus laevis / Q000378:metabolism
D002352:Carrier Proteins; D005656:Fungal Proteins; D009687:Nuclear Proteins; D012261:Ribonucleoproteins; C470475:UTP4 protein, human; D049452:Green Fluorescent Proteins