Cytokine-like proteins

Abstract

A full-length cDNA corresponding to an EST (AA418955), which does not show any homology to other proteins in the database but has a weak homology to G-CSF, has been successfully isolated by synthesizing primers based on the EST sequence, and effecting PCR-cloning from a human fetal spleen library. Sequencing of the thus-isolated cDNA and analysis of its structure revealed that the cDNA has typical characteristics of a factor belonging to the IL-6/G-CSF/MGF family. It is also found out that the culture supernatant of said sequence-transfected CHO cells shows a proliferation supporting activity towards bone marrow cells in the coexistence of kit ligand.

1 . A substantially pure polypeptide comprising the sequence of SEQ ID NO:1. 
     
     
         2 . A method of screening for a compound that binds to a polypeptide, the method comprising: contacting a test compound with the polypeptide of  claim 1 ; determining whether the test compound binds to the polypeptide; and selecting a test compound that binds to the polypeptide. 
     
     
         3 . A method of screening for a compound that promotes or inhibits proliferation of a bone marrow cell, the method comprising: contacting a mammalian bone marrow cell with the polypeptide of  claim 1  and a kit ligand, in the presence of a test compound;
 evaluating the proliferation of the bone marrow cell; and selecting a test compound that promotes or inhibits the proliferation of the bone marrow cell compared to a control. 
 
     
     
         4 . An isolated nucleic acid comprising a sequence encoding a polypeptide comprising the amino acid sequence of SEQ ID NO: 1. 
     
     
         5 . A vector comprising the nucleic acid of  claim 4 . 
     
     
         6 . A cultured host cell comprising the nucleic acid of  claim 4 . 
     
     
         7 . A method of producing a polypeptide comprising the amino acid sequence of SEQ ID NO: 1, the method comprising culturing the cultured host cell of  claim 6  in a culture, expressing the polypeptide in the cultured host cell, and isolating the polypeptide from the culture. 
     
     
         8 . An isolated antibody that specifically binds to a polypeptide consisting of the amino acid sequence of SEQ ID NO: 1, wherein the antibody recognizes an epitope within a region of the polypeptide defined by residues 24 to 38 or 74 to 88 of SEQ ID NO:1. 
     
     
         9 . A compound that promotes an activity of a polypeptide consisting of the sequence of SEQ ID NO:1. 
     
     
         10 . The compound of  claim 9 , wherein the activity is supporting proliferation of bone marrow cells in the presence of the kit ligand. 
     
     
         11 . A pharmaceutical composition comprising the compound of  claim 9  as an active ingredient. 
     
     
         12 . The compound of  claim 9 , wherein the compound is obtained by a method comprising:
 contacting a mammalian bone marrow cell with a polypeptide comprising the sequence of SEQ ID NO:1 and a kit ligand, in the presence of a test compound;   detecting proliferation of the bone marrow cell; and   selecting the test compound If it promotes the proliferation of the bone marrow cell in comparison with a bone marrow cell cultured in the absence of the test compound.   
     
     
         13 . A compound that inhibits an activity of a polypeptide consisting of the sequence of SEQ ID NO:1. 
     
     
         14 . A pharmaceutical composition comprising the compound of  claim 13  as an active ingredient. 
     
     
         15 . The compound of  claim 13 , wherein the compound is obtained by a method comprising:
 contacting a mammalian bone marrow cell with a polypeptide comprising the sequence of SEQ ID NO:1 and a kit ligand, in the presence of a test compound;   detecting proliferation of the bone marrow cell; and   selecting the test compound If it inhibits the proliferation of the bone marrow cell in comparison with a bone marrow cell cultured in the absence of the test compound.   
     
     
         16 . A compound that specifically binds to a polypeptide consisting of the sequence of SEQ ID NO:1. 
     
     
         17 . A pharmaceutical composition comprising the compound of  claim 16  as an active ingredient. 
     
     
         18 . The compound of  claim 16 , wherein the compound is obtained by a method comprising:
 contacting a test compound with a polypeptide comprising the sequence of SEQ ID NO:1;   determining whether the test compound binds to the polypeptide; and   selecting the test compound If it binds to the polypeptide.