Characterization of alternatively spliced human SP-10 mRNAs.
Alternatively spliced mRNAs encoding the human intraacrosomal protein SP-10 were sought by the reverse transcriptase polymerase chain reaction (RTPCR). Eleven RTPCR products were identified, characterized, and found to represent authentic alternatively spliced SP-10 mRNAs. The 11 alternatively spliced SP-10 mRNAs encoded proteins ranging from 81 to 265 amino acids. The 10 smaller variants all resulted from one or two in-frame deletions in exons 2 and/or 3 of the SP-10 genomic sequence. Quantitative competitive RTPCR showed that the four largest SP-10 mRNAs represented the majority (> 99%) of the SP-10 message in testes from each of four men. The relative abundance of each of the four SP-10 mRNAs varied between individuals, but the longest SP-10 mRNA, SP10-1, which encoded a 265 amino acid protein, was consistently the most abundant, comprising 53-72% of the total SP-10 message. This was followed by the second largest SP-10 mRNA, SP10-2, which encoded a protein of 246 amino acids and comprised 15-32%. The third and fourth largest SP-10 mRNAs, SP10-3 and SP10-4, encoded proteins of 210 and 195 amino acids and accounted for 3.4-8.3% and 8.7-12.5% of the total SP-10 messages, respectively. The remaining 7 SP-10 mRNAs combined accounted for < 1% of the total SP-10 message. Within the low abundance group of mRNAs were two that deleted the entire third exon of SP-10. The present study suggests that phenomena of cryptic splicing and exon skipping occur within the SP-10 mRNA. Along with proteolysis, alternative splicing also helps to explain the heterogeneous forms of SP-10 that have been observed on Western blots of human sperm extracts.
Freemerman
A J
AJ
Department of Cell Biology, University of Virginia, Charlottesville 22908, USA.
Flickinger
C J
CJ
Herr
J C
JC
D000177:Acrosome; D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000941:Antigens; D001483:Base Sequence; D012739:Gonadal Steroid Hormones; D006801:Humans; D008297:Male; D008565:Membrane Proteins; D008969:Molecular Sequence Data; D011506:Proteins / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D013094:Spermatozoa / Q000378:metabolism*
C512729:ACRV1 protein, human; D000941:Antigens; D012739:Gonadal Steroid Hormones; D008565:Membrane Proteins; D011506:Proteins; D012333:RNA, Messenger