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Coding potential of transfected human placental lactogen genes
D Reséndez-Pérez1, R Ramírez-Solís, A Varela-Echavarría
1Departamento de Bioquímica, Facultad de Medicina de la Universidad Autónoma de Nuevo León, Monterrey, Mexico.
Nucleic Acids Research
|August 25, 1990
Summary
Human placental lactogen (hPL) gene expression was investigated. Researchers found that hPL-3 and hPL-4 genes produce mature hPL, while hPL-1 does not, with hPL-3 showing higher activity.
Area of Science:
- Molecular biology
- Genetics
- Biochemistry
Background:
- The human placental lactogen (hPL) gene family plays a crucial role in pregnancy.
- Understanding the differential expression and function of hPL genes is essential for reproductive biology.
- Previous studies suggested potential functional differences among hPL gene variants.
Purpose of the Study:
- To investigate the expression and contribution of individual human placental lactogen (hPL) genes (hPL-1, hPL-3, and hPL-4) to mature hPL production.
- To identify the genetic elements responsible for the differential expression of hPL genes.
- To elucidate the reasons for the apparent inactivity of the hPL-1 gene.
Main Methods:
- Promoter-less hPL gene sequences (hPL-1, hPL-3, hPL-4) were ligated to strong transcriptional control elements.
- Cells were transfected with these constructs and labeled in vivo with 35S-methionine.
- Proteins secreted into the culture medium were analyzed using SDS-polyacrylamide gel electrophoresis and autoradiography.
- Exon-shuffling experiments were performed between hPL and human growth hormone (hGH) genes.
- Site-directed mutagenesis was used to revert the splice mutation in the hPL-1 gene.
Main Results:
- Transfection and expression studies revealed that hPL-3 and hPL-4 genes contribute to mature hPL production, whereas hPL-1 does not.
- hPL-3 demonstrated higher RNA and protein expression levels compared to hPL-4.
- Exchanging the first two exons between hPL and hGH genes indicated that these exons significantly influence chimeric protein abundance.
- Reversion of the splice mutation (G to A) in the hPL-1 gene did not restore its expression, suggesting other factors contribute to its inactivity.
Conclusions:
- hPL-3 and hPL-4 are transcriptionally active genes contributing to mature hPL production.
- The first two exons of the hPL gene play a critical role in determining protein expression levels.
- The splice mutation in hPL-1 is not the sole reason for its lack of expression; other regulatory mechanisms are involved.