Testis-specific expression of an intronless gene encoding a human poly(A) polymerase

Area of Science:

• Molecular Biology
• Evolutionary Biology
• Reproductive Biology

Background:

• A mouse testis-specific poly(A) polymerase (mPAPT) gene was identified, potentially regulating polyadenylation during spermatogenesis.
• Understanding the evolutionary conservation of PAPT genes across mammals is crucial for elucidating their function.

Purpose of the Study:

• To isolate and characterize the human homolog of mPAPT (hPAPT) to investigate its conservation in mammals.
• To analyze the structural and genomic similarities and differences between human and mouse PAPT proteins and genes.

Main Methods:

• Isolation of human cDNA encoding hPAPT.
• Structural comparison of hPAPT and mPAPT.
• Genomic DNA analysis of the hPAPT gene.
• Phylogenetic analysis of PAPT gene evolution.

Main Results:

• A human cDNA homolog, hPAPT, specifically expressed in the testis, was isolated.
• hPAPT shares structural similarities with mPAPT, notably lacking C-terminal residues found in PAP II.
• The hPAPT gene is intronless, mirroring the mPAPT gene structure.
• Sequence homology between hPAPT and mPAPT is lower than between their respective PAP II counterparts.
• Phylogenetic analysis indicates PAPT genes originated from retrotransposition events post-amphibian-amniote divergence.

Conclusions:

• hPAPT is a testis-specific poly(A) polymerase with structural and genomic similarities to mPAPT.
• The low sequence homology suggests divergent evolution despite conserved intronless structure.
• PAPT genes likely evolved through retrotransposition, playing a conserved role in mammalian spermatogenesis.