The Salk Institute for Biological Studies

Shunichi Shimasaki

Nicholas C Ling

Roger C Guillemin

Frederick S Esch

Shao-Yao Ying

Naoto Ueno

An insulin-like growth factor binding protein is isolated from rat serum and partially sequenced. Using nucleotide probes based upon the amino terminal sequence of the isolated protein, the complete sequence for the 233-residue rat protein, termed IGFBP-4, is deduced, and the homologous 237-residue sequence of the human protein is separately deduced. These proteins are useful in the inhibition of cell differentiation and/or proliferation requiring IGFs and are particularly useful in combating breast cancers. Antibodies to the proteins may be employed in diagnostic assays, in purification of the protein and in the modulation of bone growth.

DNA encoding IGFBP-4

Two follistatin proteins with inhibin-like activity were isolated from porcine follicular fluid using heparin-Sepharose affinity chromatography, followed by gel filtration on Sephacryl S-200 and then six steps of high-performance liquid chromatography. The larger protein has 315 residues and is believed to be glycosylated. The smaller protein is a 288-residue, C-terminally shortened version thereof. These proteins specifically inhibit basal secretion of FSH, but not of LH, in a rat anterior pituitary monolayer culture system. The half-maximal effective dose for both is 2.5-6.0 ng/ml. Human and rat follistatins exhibit very high homology with the porcine protein, with the human differing from porcine in only 4 residues out of 315 and with the rat differing from porcine in only 8 residues out of 315. Using the porcine amino acid sequence information, cDNA clones encoding these proteins were identified from a porcine ovarian cDNA library. Then, using the porcine cDNA as a probe, the cloning and sequencing of the corresponding human and rat proteins were accomplished.

DNA encoding follistatin

Two follistatin proteins with inhibin-like activity were isolated from porcine follicular fluid using heparin-Sepharose affinity chromatography, followed by gel filtration on Sephacryl S-200 and then six steps of high-performance liquid chromatography. Each isolated molecule is a monomer having a molecular weight of at least about 32,000 daltons. Microsequencing revealed the NH.sub.2 -terminal portions both to be Gly-Asn-Cys-Trp-Leu-Arg-Gln-Ala-Lys-Asn-Gly-Arg-Cys-Gln-Val-Leu. The larger protein has 315 residues and is believed to be glycosylated. The smaller protein is a 288-residue, C-terminally shortened version thereof. These proteins specifically inhibit basal secretion of FSH, but not of LH, in a rat anterior pituitary monolayer culture system. The Half-maximal effective dose for both is 2.5-6.0 ng/ml. Human and rat follistatins exhibit very high homology with the porcine protein, with the human differing from porcine in only 4 residues out of 315 and with the rat differing from porcine in only 8 residues out of 315.

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San Diego, CA, United States of America

Shunichi Shimasaki