A polypeptide of 8500 molecular weight is described that induces the differentiation of T (thymusderived) cell and B (bone-marrow-derived) cell immunocytes in vitro, apparently via fl-adrenergic receptors and adenylate cyclase activation. This polypeptide shows a high degree of evolutionary conservation, exhibiting close structural, functional, and immunological similarity when isolated from such diverse origins as cells of mammals and higher plants. This polypeptide was detected in animal cells, yeast, bacteria, and higher plants, and so may well be a universal constituent of living cells.The isolation from bovine thymus of the polypeptide hormones thymopoietin I and II has been described previously (1 2). [We are now using the term thymopoietin (3) because valid objections (4) were raised to our previous term "thymin," which is easily confused with the pyrimidine base thymine. ] Pure thymopoietin I and II specifically induce prothymocytes to differentiate into thymocytes (5-7), but these polypeptides were recognized originally not by this evidently physiological faculty of T (thymus-derived) cell differentiation but by a presumably incidental property discovered in the course of studies related to the human disease myasthenia gravis, in which a characteristic neuromuscular disturbance is consistently associated with thymic pathology. When reliable assays of T-cell differentiation in vitro became available, based on the manifestation of T-cell antigens on precursor cells (5,8) it was realized that, although certain pure thymic products (thymopoietins) could induce this step in T-cell differentiation specifically, extracts of tissues other than thymus were also active (10).We describe here the isolation and purification from bovine thymus of a polypeptide subsequently detected in many other tissues, which like thymopoietin induces the differentiation of pro-thymocytes, but which unlike thymopoietin induces differentiation of B (bone-marrow-derived) cells, and is thus distinguished in its mode of action from the physiological inducer thymopoietin. This The isolation of UBIP from bovine thymus is summarized in Fig. 1. Bovine thymus was obtained fresh on wet ice, dissected clean and stored at -20°. Batches were homogenized 25% wet weight/volume in 0.1 M ammonium bicarbonate with a Waring blender. The extract was heated to 700 for 30 min and then centrifuged at 500 X g for 30 min. The supernatant was filtered through gauze and cotton and 0.1% thimerosal was added as a bacteriostatic agent, since the subsequent steps were carried out at room temperature. The extract was processed through a Diaflo XM1OOA membrane (Amicon) in a TCF10 apparatus. The dialysate was then concentrated over a Diaflo UM2 membrane at 55 lb./in.2, using a 402 stirred cell and a reservoir; 3 liters were concentrated to 15 ml. This retentate was fractionated on a 2.5 X 100-cm column of medium Sephadex G-50 (Pharmacia) in 0.1 M ammonium bicarbonate. The fractions shown in Fig. 1 were lyophilized and rerun on the same column. The lyophili...

Epidermal growth factor (EGF), a protein comprising 53 amino acids, is derived from a precursor of 1,217 amino acids that includes at least seven EGF-like sequences. EGF has diverse biological activities: it is a potent mitogen for many tissue culture cells, inhibits gastric acid secretion from the intestinal mucosa and promotes healing of the corneal epithelium. EGF given to fetal animals accelerates several developmental processes including palate formation, incisor eruption, eyelid opening and lung maturation. However, the physiological roles of EGF in vivo are unknown. The presence of high-affinity receptors in many fetal and adult tissues suggests that EGF is involved in normal cellular functions. Immunocytochemical studies have revealed the presence of EGF in mouse and human submaxillary glands, rat brain and human intestine. The low levels of EGF in extracts from many tissues may reflect sequestration rather than synthesis of the polypeptide. We show here that several mouse tissues contain preproEGF mRNA and that it is synthesized mainly in the distal tubules of the kidney. PreproEGF does not seem to be processed to EGF or other peptides in this tissue.

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In earlier studies we identified in a human genomic library a gene (human relaxin gene HI) coding for a relaxin-related peptide. We now have evidence that the human genome possesses an additional relaxin-related gene (designated human relaxin gene H2) which appears to be selectively expressed in the ovary during pregnancy. Nucleotide sequence analysis revealed striking differences in the predicted structures of relaxin encoded by these two genes. Chemical synthesis of biologically active relaxin based on the sequence obtained from ovarian cDNA clones confirmed that the expressed gene (H2) encodes an authentic human relaxin. The expressed gene appears to be transcribed into two different sized mRNAs and preliminary evidence suggests that the mRNA transcripts possess different 3'-untranslated regions. There was no evidence for the expression of human relaxin gene HI in the ovary and so far it is unclear whether gene Hl is expressed in another tissue or whether it represents a pseudogene. From the sequence data presented here it will now be possible to construct oligonucleotide probes and raise antibodies against synthetic peptides which could then be used to identify sites of relaxin biosynthesis and specifically quantitate the expression from either the Hl or H2 relaxin genes.

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