Hypoxanthine-guanine phosphoribosyltransferase (HPRT, EC 2.4.2.8) is a purine salvage enzyme that catalyses the conversion of hypoxanthine and guanine to their respective mononucleotides. Partial deficiency of this enzyme can result in the overproduction of uric acid leading to a severe form of gout, whilst a virtual absence of HPRT activity causes the Lesch-Nyhan syndrome which is characterised by hyperuricaemia, mental retardation, choreoathetosis and compulsive self-mutilation. The HPRT-encoding gene is located on the X chromosome in the region q26-q27 and consists of nine exons and eight introns totalling 57 kb. This gene is transcribed to produce an mRNA of 1.6 kb, which contains a protein encoding region of 654 nucleotides. With the advent of increasingly refined techniques of molecular biology, it has been possible to study the HPRT gene of individuals with a deficiency in HPRT activity to determine the genetic basis of the enzyme deficiency. Many different mutations throughout the coding region have been described, but in the absence of precise information on the three-dimensional structure of the HPRT protein, it remains difficult to determine any consistent correlation between the structure and function of the enzyme.

SUMMARYP3HR-1 and Ramos cells induced with sodium butyrate and 12-O-tetradecanoylphorbol 13-acetate were used in the protein immure,blot technique to identify EpsteinBarr virus (EBV)-specific antibodies present in ser~ from clinically normal individuals and patients with systemic lupus erythematosus (SI,E), rheumatoid arthritis (RA) and infectious mononucleosis (IM). Sixteen EBV-sp,'cific polypeptides were detected ranging in tool. wt. from 22000 (22K) to 140K. Many of the sera contained antibodies to different subsets of these antigens, and a high pJ oportion expressed autoantibodies which reacted with cellular components from an EB V genome-negative cell line. About 50% of the sera from each category reacted with the 44K to 48K and 36K and 38K early antigen (EA) components. A high proportion of 1he SLE sera (64~) were found to contain anti-EA antibodies, suggesting an associati on between EBV and SLE. Almost all of the EBV-seropositive sera examined contai ned antibodies against a 22K late antigen, but none of the sera from IM patients r~ acted with this polypeptide.

SUMMARYThe protein immunoblot technique was used to identify Epstein-Barr virus-specific antigens present in sodium butyrate-induced P3HR-1 cells. Using sera from patients with either nasopharyngeal carcinoma or arthritis, 16 polypeptides were detected ranging in molecular weight from 22K to 140K. Each of the anti-EA-, anti-VCApositive sera were found to contain antibodies to different subsets of the antigens. A 72K protein was identified which was consistent with the nuclear antigen (EBNA), and culturing cells in the presence of disodium phosphonoacetate allowed identification of 140K and 22K antigens as late viral products. Treatment of cells with sodium butyrate revealed that expression of some antigens increased in parallel with the time of incubation of the cells in butyrate while other antigens either appeared early and then decreased in intensity or were only present after a number of days of butyrate treatment. One of the antigens which decreased with the time cells were treated with butyrate was EBNA.

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