Rat probasin: structure and function of an outlier lipocalin

Area of Science:

• Molecular Biology
• Genomics
• Biochemistry

Background:

• Probasin (PB) is a protein abundant in rat prostate epithelial cells, functioning both as a secreted and nuclear protein.
• The rat probasin gene shares structural similarities with other lipocalin superfamily members, including exon number and size.

Purpose of the Study:

• To characterize the genomic structure of the rat probasin gene.
• To identify conserved motifs and structural features of the probasin protein.
• To investigate the regulatory mechanisms of probasin gene expression.

Main Methods:

• Isolation and characterization of a rat probasin gene genomic clone.
• Sequence alignment and motif analysis of deduced amino acids.
• Analysis of the 5'-flanking region for regulatory elements.

Main Results:

• The rat probasin gene consists of seven exons, with splice sites conforming to the GT/AG consensus.
• Probasin contains conserved motifs (G-X-W, C-X-X-X-C) and structural features (beta-sheets, alpha-helix) characteristic of the lipocalin superfamily.
• Unique features include a large genomic fragment and a highly basic isoelectric point (pI 11.5).
• Probasin gene expression is regulated by androgens and zinc, with androgen receptor binding sites identified in the 5'-flanking region.

Conclusions:

• The rat probasin gene exhibits characteristics of the lipocalin superfamily but possesses unique features.
• Androgens and zinc are key regulators of probasin gene expression in the prostate.
• The identified regulatory elements facilitate androgen-specific and prostate-specific transgene expression.