Transcription of the human and rodent SPAM1 / PH-20 genes initiates within an ancient endogenous retrovirus.
BACKGROUND
Sperm adhesion molecule 1 (SPAM1) is the major mammalian testicular hyaluronidase and is expressed at high levels in sperm cells. SPAM1 protein is important for penetration of the cumulus cell layer surrounding the ovum, and is also involved in zona pellucida binding and sperm intracellular signalling. A previous study had identified SPAM1 as one of the many human genes that initiate within a transposable element.


RESULTS
Examination of the human, mouse and rat SPAM1 loci revealed that transcripts initiate within the pol gene of an endogenous retrovirus (ERV) element. This is highly unusual, as all previously identified ERV-initiated cellular gene transcripts initiate within the viral long terminal repeat promoter. The SPAM1 locus therefore represents an example of the evolution of a promoter from protein-coding sequence. We have identified novel alternative promoter and splicing variants of human and murine SPAM1. We show that all transcript variants are expressed primarily in the testis and are predicted to encode identical proteins.


CONCLUSIONS
The testis-specific promoters of the human and mouse SPAM1 genes are derived from sequence that was originally part of an ERV pol gene. This represents the first known example of an ERV-derived promoter acting in a gender-specific manner.
Dunn
Catherine A
CA
Terry Fox Laboratory, BC Cancer Agency, Vancouver, Canada. cdunn@bccrc.ca
Mager
Dixie L
DL
D017398:Alternative Splicing; D000818:Animals; D001483:Base Sequence; D015815:Cell Adhesion Molecules / Q000096:biosynthesis* / Q000235:genetics*; D019295:Computational Biology / Q000379:methods; D017931:DNA Primers / Q000737:chemistry; D004251:DNA Transposable Elements; D020077:Endogenous Retroviruses / Q000235:genetics*; D005260:Female; D005786:Gene Expression Regulation; D023281:Genomics / Q000379:methods; D006801:Humans; D006821:Hyaluronoglucosaminidase / Q000096:biosynthesis* / Q000235:genetics*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008969:Molecular Sequence Data; D010766:Phosphorylation; D011401:Promoter Regions, Genetic; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012737:Sex Factors; D015398:Signal Transduction; D012984:Software; D013737:Testis / Q000378:metabolism
D015815:Cell Adhesion Molecules; D017931:DNA Primers; D004251:DNA Transposable Elements; D006821:Hyaluronoglucosaminidase; C066852:hyaluronidase PH-20