The newly identified human nuclear protein NXP-2 possesses three distinct domains, the nuclear matrix-binding, RNA-binding, and coiled-coil domains.
Using a monoclonal antibody that recognizes a nuclear matrix protein, we selected a cDNA clone from a lambdagt11 human placenta cDNA library. This cDNA encoded a 939-amino acid protein designated nuclear matrix protein NXP-2. Northern blot analysis indicated that NXP-2 was expressed in various tissues at different levels. Forcibly expressed green fluorescent protein-tagged NXP-2 as well as endogenous NXP-2 was localized in the nucleus and distributed to the nuclear matrix. NXP-2 was released from the nuclear matrix when RNase A was included in the buffer for nuclear matrix preparation. Mapping of functional domains was carried out using green fluorescent protein-tagged truncated mutants of NXP-2. The region of amino acids 326-353 was responsible for nuclear matrix binding and contained a cluster of hydrophobic amino acids that was similar to the nuclear matrix targeting signal of acute myeloleukemia protein. The central region (amino acids 500-591) was demonstrated to be required for RNA binding by Northwestern analysis, although NXP-2 lacked a known RNA binding motif. The region of amino acid residues 682-876 was predicted to have a coiled-coil structure. The RNA-binding, nuclear matrix-binding, and coiled-coil domains are structurally separated, suggesting that NXP-2 plays important roles in diverse nuclear functions, including RNA metabolism and maintenance of nuclear architecture.
Kimura
Yukio
Y
Department of Life Science, Graduate School and Faculty of Science, Himeji Institute of Technology, Kamigori, Hyogo 678-1201, Japan.
Sakai
Fumie
F
Nakano
Osami
O
Kisaki
Osamu
O
Sugimoto
Hiroaki
H
Sawamura
Takashi
T
Sadano
Hiroyuki
H
Osumi
Takashi
T
D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D002460:Cell Line; D049452:Green Fluorescent Proteins; D006801:Humans; D008164:Luminescent Proteins / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D008969:Molecular Sequence Data; D015530:Nuclear Matrix / Q000378:metabolism*; D011487:Protein Conformation; D016601:RNA-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D017386:Sequence Homology, Amino Acid
D008164:Luminescent Proteins; D016601:RNA-Binding Proteins; D011993:Recombinant Fusion Proteins; D049452:Green Fluorescent Proteins