Subcellular localization of ribosomal P0-like protein MRT4 is determined by its N-terminal domain.
The Mrt4 protein, showing extensive sequence similarity to the ribosomal P0 protein, is classified as a ribosomal P0-like protein and acts as a trans-acting factor which modulates the assembly of the pre-60S particle. In this report we investigated the biological nature of the human Mrt4 protein. First, we constructed a series of hybrid hMrt4-P0 proteins by replacing various domains of the P0 protein with corresponding protein fragments from hMrt4. We found that hMrt4 binds to the same site on the large ribosomal subunit as does P0, but despite the sequence homology it is not able to functionally complement the lack of P0. Using fluorescence microscopy and biochemical approaches we also show that hMrt4 occupies predominantly the nucleolar compartment, in contrast to P0 and P1/P2, which are located in the cytoplasm. The nucleolar accumulation of hMrt4 does not depend on a specific nucleolus localization signal, but rather occurs via interaction with established nucleolar components such as rRNA; however, nuclear import of hMrt4 is dependent on a short sequence in the N-terminal part of the protein. Functional analysis with specific inhibitors, actinomycin D and leptomycin B, showed that hMrt4 is a trans-acting factor involved in ribosome maturation, with nucleus-cytoplasm shuttling capacity.
Michalec
Barbara
B
Department of Molecular Biology, Maria Curie-Skłodowska University, Akademicka 19, 20-033 Lublin, Poland.
Krokowski
Dawid
D
Grela
Przemysław
P
Wawiórka
Leszek
L
Sawa-Makarska
Justyna
J
Grankowski
Nikodem
N
Tchórzewski
Marek
M
D000818:Animals; D001665:Binding Sites; D002466:Cell Nucleolus / Q000378:metabolism*; D003593:Cytoplasm / Q000378:metabolism; D017930:Genes, Reporter; D006367:HeLa Cells; D006801:Humans; D051379:Mice; D041681:NIH 3T3 Cells; D054730:Protein Interaction Domains and Motifs / Q000235:genetics; D021381:Protein Transport; D012323:RNA Processing, Post-Transcriptional; D012335:RNA, Ribosomal / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012269:Ribosomal Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D054683:Ribosome Subunits, Large, Eukaryotic / Q000378:metabolism; D012270:Ribosomes / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D016415:Sequence Alignment; D015534:Trans-Activators / Q000378:metabolism
D012335:RNA, Ribosomal; D016601:RNA-Binding Proteins; D011993:Recombinant Fusion Proteins; D012269:Ribosomal Proteins; D029701:Saccharomyces cerevisiae Proteins; D015534:Trans-Activators; C121972:MRT4 protein, S cerevisiae; C549920:MRTO4 protein, human; C054675:ribosomal protein P0