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R D Sege

Publications and source records attributed to R D Sege.

4 recordsLinked to original sources
PubMed1986

DNA-mediated transfer of a human gene required for low-density lipoprotein receptor expression and for multiple Golgi processing pathways.

Transfection of a hamster cell mutant with human DNA corrected both the low-density lipoprotein receptor-deficient phenotype and the multiple glycosylation defects of the cells. Independently transfected colonies contained a small set of common human DNA fragments. These fragments may correspond to the human analog of a single gene required for several different Golgi processing pathways.

Animals↗
PubMed1986

Characterization of a family of gamma-ray-induced CHO mutants demonstrates that the ldlA locus is diploid and encodes the low-density lipoprotein receptor.

The ldlA locus is one of four Chinese hamster ovary (CHO) cell loci which are known to be required for the synthesis of functional low-density lipoprotein (LDL) receptors. Previous studies have suggested that the ldlA locus is diploid and encodes the LDL receptor. To confirm this assignment, we have isolated a partial genomic clone of the Chinese hamster LDL receptor gene and used this and other nucleic acid and antibody probes to study a family of ldlA mutants isolated after gamma-irradiation. Our analysis suggests that there are two LDL receptor alleles in wild-type CHO cells. Each of the three mutants isolated after gamma-irradiation had detectable deletions affecting one of the two LDL receptor alleles. One of the mutants also had a disruption of the remaining allele, resulting in the synthesis of an abnormal receptor precursor which was not subject to Golgi-associated posttranslational glycoprotein processing. The correlation of changes in the expression, structure, and function of LDL receptors with deletions in the LDL receptor genes in these mutants directly demonstrated that the ldlA locus in CHO cells is diploid and encodes the LDL receptor. In addition, our analysis suggests that CHO cells in culture may contain a partial LDL receptor pseudogene.

Amino Acid Sequence↗
PubMedDate not supplied

Expression and regulation of human low-density lipoprotein receptors in Chinese hamster ovary cells.

Low-density lipoprotein (LDL), the major cholesterol transport component of human plasma, delivers cholesterol to mammalian cells via the LDL pathway of receptor-mediated endocytosis. LDL receptor activity and cholesterol biosynthesis are coordinately regulated by cholesterol-mediated feedback suppression. We have developed methods for the isolation of mutant and revertant (M.K., unpublished data) Chinese hamster ovary (CHO) cells having alterations in cholesterol biosynthesis and in the receptor-mediated endocytosis of LDL. The defective locus of one LDL receptor-negative CHO mutant (clone 7a-1) is apparently the structural gene for the LDL receptor (D. Kingsley, M. Segal and M.K., unpublished data). Here we have transfected 7a-1 cells with human DNA and selected colonies which synthesize functional human LDL receptors whose expression is regulated normally. This selection may prove useful for cloning genes required for the receptor-mediated endocytosis of LDL and other ligands and thus for elucidating the molecular defects responsible for familial hypercholesterolaemia, one of the most common genetic diseases in humans.

Animals↗