Organization of the human cholesteryl ester transfer protein gene

The plasma cholesteryl ester transfer protein (CETP) catalyzes the transfer of phospholipids and neutral lipids between the lipoproteins. Thus, this protein may be important in modulating lipoprotein levels in the plasma. We have determined the primary structure and organization of the human CETP gene. Southern blotting of cellular DNA indicated a single copy of the CETP gene exists per haploid genome. Analysis of three overlapping genomic clones showed that the gene spans approximately 25 kbp and contains 16 exons (size range 32-250 bp). Overall, the sequence and organization of the CETP gene do not resemble those of other lipid-metabolizing enzymes or apolipoproteins. However, comparison of the CETP sequence, one exon at a time, with the sequences in the sequence databases revealed a striking identity of a pentapeptide sequence (ValLeuThrLeuAla) within the hydrophobic core of the signal sequences of human CETP, apolipoproteins A-IV and A-I, and lipoprotein lipase. This pentapeptide sequence was not found in the signal sequences of other proteins, suggesting that it may mediate a specialized function related to lipid metabolism or transport.     

Assignment of the gene locus for human phosphoglucomutase 3 to chromosome 6q12-qter

Segregation of human PGM3 has been analyzed in somatic cell hybrids between mouse A9 cells and human fibroblasts carrying a reciprocal translocation: 46,XX, t(6;7) (q12;p14). The enzyme marker segregates with the 7p+ chromosome indicating that the PGM3 gene is located on 6q12 greater than qter.     

Assignment of the human gene for phosphoglycolate phosphatase to chromosome 16

Summary Seventeen independently derived primary mouse-human hybrid clones were scored for the expression of human phosphoglycolate phosphatase (PGP) by electrophoresis and for the presence of human chromosomes with the aid of Q banding. The correlation of biochemical and cytogenetic analyses shows that the segregation of human PGP in these hybrids is concordant only with human chromosome 16, thus enabling the assignment of the genetic locus for PGP to human chromosome 16.     

Assignment of the myelin basic protein gene to human chromosome 18q22-qter

Summary The assignment of the human myelin basic protein gene to 18q22-qter has been made using a mouse cDNA probe in the study of human-mouse somatic cell hybrids and by in situ hybridization. These results confirm the earlier assignment using in situ studies alone by Saxe et al. (1985).     

Assignment of the human tyrosine aminotransferase gene to chromosome 16

Summary The liver enzyme tyrosine aminotransferase (TAT; EC 2.6.1.5) catalyzes the rate-limiting step in the catabolic pathway of tyrosine. Deficiency in TAT enzyme activity underlies the autosomally inherited disorder tyrosinemia II (Richner-Hanhart syndrome). Using a human TAT cDNA clone as hybridization probe, we have determined the chromosomal location of the TAT structural gene by Southern blot analysis of DNAs from a series of human x rodent somatic cell hybrids. The results assign the TAT gene to human chromosome 16.     

Assignment of the human antithrombin III structural gene to chromosome 1q23-25

The human antithrombin III (ATIII) structural gene was mapped by in situ hybridization and quantitative analysis of ATIII gene dosage in DNA isolated from carriers of chromosome 1 deletions. These studies indicate that the ATIII structural gene maps to human chromosome q23-q25 and so is likely identical to AT3.     

Monoclonal antibodies to the Mr 74,000 cholesteryl ester transfer protein neutralize all of the cholesteryl ester and triglyceride transfer activities in human plasma

A cholesteryl ester transfer protein (CETP) of apparent Mr 74,000 has recently been purified from human plasma. Three monoclonal neutralizing antibodies to the CETP were obtained by immunizing mice with purified CETP. The antibodies, each recognizing a similar epitope on CETP, caused parallel and complete immunotitration of plasma cholesteryl ester and triglyceride transfer activities but only partial inhibition of phospholipid transfer activity. Monoclonal immunoaffinity chromatography of plasma or its fractions showed complete removal of cholesteryl ester and triglyceride transfer activities but incomplete removal of phospholipid transfer activity. Sodium dodecyl sulfate gel electrophoresis and immunoblotting of the immunoaffinity-retained fractions showed that only the Mr 74,000 protein was immunoreactive. The results suggest that the previously characterized CETP accounts for all of the cholesteryl ester and triglyceride transfer activity in human plasma but only part of the phospholipid transfer activity.     

Assignment of the gene for human spasmolytic protein (hSP/SML1) to chromosome 21

Summary A human cDNA corresponding to the porcine pancreatic spasmolytic protein (PSP) was isolated, and the recombinant clone was originally termed hSP for human spasmolytic protein. Later, the term SML1 for spasmolysin was suggested for the human gene. This protein shows a remarkable sequence homology to pS2, a protein coded by an estrogen-induced gene isolated from the breast carcinoma cell line MCF-7. Although, at the DNA level, the gene sequences pS2 and hSP/SML1 display insufficient homology for cross-hybridization, their expression in tumor cells occurs with remarkable coordination. The human pS2 gene sequence has been assigned to chromosome 21, and we have therefore attempted to map the hSP/SMLl gene by using cDNA and Southern blotting of genomic DNAs from a panel of human-rodent somatic cell hybrids carrying different complements of human chromosomes. Interestingly, the hSP/SMLl gene is also localized on chromosome 21.     

Establishment of anti-human cholesteryl ester transfer protein monoclonal antibodies and radioimmunoassaying of the level of cholesteryl ester transfer protein in human plasma.

Plasma cholesteryl ester transfer protein (CETP) facilitates the net transfer and exchange of cholesteryl ester (CE), triglyceride (TG), and phospholipids between lipoproteins. A series of monoclonal antibodies (mAbs) against human CETP was obtained, comprising mAbs either inhibiting or not inhibiting these transfer activities. One mAb (LT-J1) inhibited the transfer activity of TG almost completely, but not that of CE, indicating that CE and TG binding sites on the CETP molecule may be distinct from each other, and that this mAb may specifically recognize the TG binding site. A radioimmunoassay system for determining the level of CETP was also established using these mAbs, and the plasma CETP levels in 20 normolipemic Japanese adults were found to range from 2.1 to 2.7 mg/liter.     

Assignment of the human protein C gene (PROC) to chromosome region 2q14----q21 by in situ hybridization

The protein C gene (PROC) was mapped by in situ hybridization. A genomic DNA probe containing the first three exons was 3H-labeled by nick translation, and this was then hybridized in situ to human chromosome preparations. The results localize the gene to 2q14----q21.     

Assignment of the human glycogen debrancher gene to chromosome 1p21

Glycogen debranching enzyme is a monomeric protein containing two independent catalytic activities of glycantransferase and glucosidase that are both required for glycogen degradation. Its deficiency causes type III glycogen storage disease. A majority of the patients with this disease have deficient enzyme activity in both liver and muscle (type IIIa) but approximately 15% of them lack enzyme activity only in the liver (type IIIb); however, the enzyme is a monomer and appears to be identical in all the tissues. The cDNA coding for the complete human muscle debranching enzyme has recently been isolated. Using the cDNA clones, the debrancher gene was localized to human chromosome 1 by somatic cell hybrid analysis. Regional assignment to chromosome band 1p21 was determined by in situ hybridization. Mapping of the debrancher gene to a single chromosome site is consistent with our hypotheses that a single gene encodes both liver and muscle debrancher protein.