PubMed Health⌕ Search

Biomedical subjects

S Chada

Publications and source records attributed to S Chada.

42 records · Page 3Linked to original sources
PubMed1990

Isolation and chromosomal localization of the human glutathione peroxidase gene.

We have isolated cDNA clones for the gene, termed GPX1, encoding the major human selenoprotein, glutathione peroxidase. Sequence analysis confirmed previous findings that the unusual amino acid seleno-cysteine is encoded by the opal terminator codon UGA. Southern blot analysis of human genomic DNA with the GPX1 cDNA showed that restriction endonucleases without sites in the probe sequence produced three hybridizing bands at standard stringency, diminishing to one strongly and one weakly hybridizing band at high stringency. In situ hybridization localized the human GPX1 gene to a single site on chromosome 3, at region 3q11-13.1. Thus, three genomic sites bear sequence homology to the GPX1 cDNA, and the one most homologous maps to 3q11-13.1.

Base Sequence↗
PubMed1989

Post-transcriptional regulation of glutathione peroxidase gene expression by selenium in the HL-60 human myeloid cell line.

We have used a cloned cDNA for the major human selenoprotein, glutathione peroxidase (GPx), to assess the mode of regulation of human GPx gene (GPX-1) expression by selenium. When the HL-60 human myeloid cell line is grown in a selenium-deficient medium, GPx enzymatic activity decreases 30-fold compared with selenium-replete cells. Upon return to a medium containing selenium in the form of selenite, GPx activity in the cells starts to increase within 48 hours and reaches maximal (selenium-replete) levels at 7 days. Steady-state immunoreactive protein levels correlate with enzymatic activity. Cycloheximide inhibits the rise in GPx activity that accompanies selenium replenishment, indicating that protein synthesis is required for the increase. However, GPx mRNA levels and the rate of transcription of the human GPx gene change very little and thus appear to be independent of the selenium supply. Thus the human GPx gene appears to be regulated post-transcriptionally, probably cotranslationally, in response to selenium availability.

Blotting, Western↗
PubMed1989

Differentiation of human hematopoietic cells increases expression of a gene transferred by a retroviral vector.

To study expression of a retroviral vector in human hematopoietic lineages, two established human hematopoietic cell lines (HL60 and K562) and a human adherent stromal cell line (KM101) were infected with the vector pZIP-SV(X). Expression of the transferred neomycin resistance gene (neor) of pZIP-SV(X) was evaluated as the ability of the cells to form colonies (greater than 50 cells) in an agar assay in the presence of the neomycin analogue, G418. After infection, all three cell lines produced colonies resistant to G418. The level of neor mRNA in separate colonies was analyzed by Northern blot analysis. The neor gene transferred by the vector pZIP-SV(X) was expressed in both human hematopoietic and stromal cell lines. In addition, primary adherent human stromal cells infected with pZIP-SV(X) grew in the presence of G418. To determine if differentiation of hematopoietic cells affects expression of the retroviral vector, HL60 cells infected with pZIP-SV(X) were induced to differentiate, and the level of neor mRNA measured. The amount of neor mRNA increased when HL60 cells were induced to differentiate along the granulocytic pathway. Conversely, when HL60 cells were induced toward monocytoid differentiation (TPA), the level of neor mRNA did not significantly increase. We conclude that the neor gene transferred by a retroviral vector, pZIP-SV(X), is functionally expressed. In addition, expression of the transferred neor gene is regulated during myeloid differentiation of HL60 cells.

Cell Differentiation↗
PubMed1987

mRNA species regulated during the differentiation of HL-60 cells to macrophages and neutrophils.

Using cDNA clone banks from differentiated and undifferentiated HL-60 promyelocytic leukemia cells, we have selected clones for genes which are regulated during this differentiation. Regulation of the corresponding mRNAs in HL-60 cells during both monocytic and neutrophilic differentiation was measured for 21 of these clones. The levels of mRNA hybridizing to some of these clones changed by more than 100-fold during differentiation. Unlike erythropoiesis or myogenesis, in which the synthesis of a few new proteins is synchronously regulated, mRNAs in differentiating HL-60 cells are asynchronously regulated, suggesting a complex series of regulatory events. About half of these regulation-selected clones contained repeat sequences, including both Alu and novel repeat families. Most of the regulated genes are members of extensive gene families.

Cell Differentiation↗
PubMed1986

Structure and expression of ferritin genes in a human promyelocytic cell line that differentiates in vitro.

HL-60 is a human promyelocytic cell line with the capability of differentiating in vitro to give neutrophils, macrophages, or eosinophils. We screened libraries of HL-60 cDNA clones representing different time points during these differentiation processes to isolate clones corresponding to mRNAs whose expression is regulated during terminal differentiation. Upon sequencing this group of regulated clones, one clone encoding the heavy subunit and two clones encoding the light subunit of human ferritin were identified by reference to published amino acid sequences. Southern blot analyses showed that these clones are encoded by distinct multigene families. These clones identify two mRNAs whose ratios vary in a complex manner during both neutrophil and macrophage differentiation.

Amino Acid Sequence↗