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L Belanger

Publications and source records attributed to L Belanger.

12 recordsLinked to original sources
PubMed1992

Molecular cloning of two C/EBP-related proteins that bind to the promoter and the enhancer of the alpha 1-fetoprotein gene. Further analysis of C/EBP beta and C/EBP gamma.

In an attempt to identify proteins that may regulate alpha 1-fetoprotein (AFP) gene expression, we screened a cDNA expression library from neonatal rat liver with two essential cis-elements of the AFP promoter and enhancer. We isolated two cDNAs which were found to correspond to leucine zipper proteins of the CC-AAT/enhancer binding protein (C/EBP) family: C/EBP beta and C/EBP gamma. The three related proteins C/EBP alpha, beta and gamma bind with indistinguishable specificity to multiple DNA sites in the promoter and the enhancer of the AFP gene. In addition, C/EBP beta and C/EBP gamma readily heterodimerize with each other as well as with C/EBP alpha. The mRNAs coding for C/EBP beta and C/EBP gamma are expressed in a wider variety of rat tissues than C/EBP alpha mRNA, including yolk sac and fetal liver. The steady-state levels of C/EBP alpha, beta and gamma mRNAs increase during liver development, in parallel with their respective gene transcriptional rates. The high levels of C/EBP beta and gamma mRNAs in rat yolk sac and fetal liver, where C/EBP alpha is poorly expressed, suggest that C/EBP beta and/or gamma could be preponderant or early regulators of the AFP gene in these tissues.

Amino Acid Sequence↗
PubMed1977

Rat iso-alpha1-fetoproteins. Purification and interaction with estradiol-17beta.

The combination of polyacrylamide gel electrophoresis and Concanavalin-A-Sepharose affinity chromatography has permitted the isolation on a preparative scale, of four molecular forms of rat alpha 1-fetoprotein: a "slow" and a "fast" fraction, each separable into Concanavalin-A-adsorbed ("high carbohydrate", i.e. rich in accessible alphaD-Mannosyl and alphaD-Glu-cosyl residues) and a Concanavalin-A-non adsorbed ("low carbohydrate") fractions. These four iso-alpha 1-fetoproteins (iso-AFP) bind estradiol-17beta. However, they disclose differences in both their association constants and number of binding sites for this hormone. Very high affinity sites (10(9) are mainly located on the "slow-low carbohydrate" form. Low affinity, high capacity sites are preferentially located on the "high carbohydrate" form. These results confirm the molecular and functional heterogeneity of rat AFT and suggest that the carbohydrate moiety of the protein may have a role in estrogen-AFP interactions.

Animals↗
PubMed1976

Purification and interaction with estradiol-17beta.

The combination of polyacrylamide gel electrophoresis and Concanavalin-A-Sepharose affinity chromatography has permitted the isolation on a preparative scale, of four molecular forms of rat alpha1-fetoprotein: a "slow" and a "fast" fraction, each separable into Concanavalin-A-adorbed ("high carbohydrate", i.e. rich in accessible alphaD-Mannosyl and alphaD-Glucosyl residues) and a Concanavalin-A-non adsorbed ("low carbohydrate") fractions. These four iso-alpha-fetoproteins (iso-AFP) bind estradiol-17beta. However, they disclose differences in both their association constants and number of binding sites for this hormone. Very high affinity sites (10(9)) are mainly located on the "slow-low carbohydrate" form. Low affinity, high capacity sites are preferentially located on the "high carbohydrate" form. These results confirm the molecular and functional heterogeneity of rat AFP and suggest that the carbohydrate moiety of the protein may have a role in estrogen-AFP interactions.

Animals↗
PubMed1976

Double-antibody enzyme immunoassay applied to human alpha 1-fetoprotein.

We report the development of a double-antibody system for enzyme immunoassay of human alpha 1-fetoprotein. Equilibrium and sequential saturation procedures were evaluated and compared with a similar double-antibody radioimmunoassay. With our method, 3 mug of alpha 1-fetoprotein per liter can be detected. The dose-response curve covers a 100-fold range of analyte concentrations. Within-run and between-run coefficients of variation are respectively 6.9% and 10.0%. Analytical recovery of added antigen is 99.5 +/- 10.6%. Results are routinely obtained in 24 h but can be obtained in less than 8 h. Alpha 1-fetoprotein was measured in a variety of clinical samples, including sera from 488 pregnant women. The advantages of the present method over radioimmunoassay and other enzyme immunoassay procedures are discussed.

Alkaline Phosphatase↗