Molecular cloning, sequence analyses, and expression of complementary DNA encoding murine progesterone receptor

Area of Science:

• Molecular endocrinology
• Genomics
• Protein biochemistry

Background:

• Progesterone receptors (PRs) exist as two main molecular forms, A and B.
• Murine tissues, particularly mammary glands, predominantly express the PR-A form.
• PR-A predominance in mice is linked to developmental regulation.

Purpose of the Study:

• To elucidate the molecular mechanisms behind PR-A form predominance in murine tissues.
• To investigate the developmental regulation of progesterone receptors in mice.
• To characterize the mouse progesterone receptor at the molecular level.

Main Methods:

• Isolation and sequencing of mouse progesterone receptor complementary DNA (cDNA).
• Nucleotide sequence analysis to identify open reading frames and predict protein characteristics.
• Expression of mouse PR cDNA in Chinese hamster ovary (CHO) cells.
• Progestin binding assays and Western blot analysis to characterize the expressed protein.

Main Results:

• Two in-frame ATG codons were identified, suggesting potential for two protein isoforms (99 kDa and 81 kDa).
• The murine PR showed high homology with human, rabbit, and chicken PRs in DNA and steroid binding domains.
• Expressed mouse PR in CHO cells bound a synthetic progestin and exhibited both A and B immunoreactive forms.

Conclusions:

• The study provides the molecular basis for the predominant PR-A form in murine tissues.
• Understanding mouse PR structure and expression is crucial for studying progesterone's role in development and disease.
• The findings contribute to the comparative analysis of progesterone receptor evolution across species.