Cloning of the Semenogelin II Gene of the Rhesus Monkey

Abstract

The semenogelin I1 gene from the rhesus monkey has been cloned and characterized. The transcription unit is split into three exons of 97, 2086 and 124 bp, with two intervening introns of 241 bp and 862 bp. The first exon codes for a 23-amino-acid signal peptide and the two amino-terminal residues of the secreted protein. The second exon codes for the rest of the mature protein, and the third exon contains non-coding nucleotides only. Secreted rhesus monkey seinenogelin I1 consists of 683 amino acid residues, has a calculated Mr of 77362, is devoid of Cys and Met, and displays a highly repetitive structure composed of ten 60-amino-acid repeats. Hybridization with genomic DNA showed that the semenogelin I1 gene of man, rhesus monkey and baboon has evolved through extension of the coding region with 360-bp segments. In contrast, the length of the semenogelin I gene of these species appears to be conserved.The two genes are also present in some New World monkeys, as was revealed by hybridization with genomic DNA from the marmoset. However, another New World monkey, the cotton-top tamarin, carries only one semenogelin gene, but also has a gene that is similar to the mouse semenoclotin gene.Keywords: semen ; transglutaminase; evolution ; coagulation ; primate.Semen is composed of secretions from the accessory sex glands and epididymal spermatozoa. Newly ejaculated human semen has the structure of a loose gel which liquefies within 5-20 min to release the entrapped spermatozoa. The major gelforming proteins are the closely related semenogelin I and I1 (SgI, SgII), primarily expressed in the seminal vesicles (Lilja and Laurel], 1984;Lilja et al., 1989;Lilja and Lundwall, 1992). The liquefaction of the gel is due to proteolytic degradation of the semenogelins (Sg) by the prostate-secreted protein prostatespecific antigen (PSA;Lilja, 1988). Semen from the rhesus monkey forms a firm gel when fluid from the seminal vesicles is mixed with secretions from the cranial lobe of the prostate (Greer, 1968;van Wagenen, 1936). The liquefaction process seen in man is not observed in the rhesus monkey; instead the spermatozoa are believed to be released by an exudation process that is completed within 40 min (van Pelt and Keyser, 1970). Little is known about the proteins constituting the gel in the rhesus monkey, although immunoreactive material recognized by antibodies raised against human SgI has been found in the seminal vesicles and in the vas deferens (Aumuller et al., 1990).It was recently shown that the genes encoding Sg and other predominant proteins secreted by the seminal vesicles, together with the gene encoding the protease inhibitor skin-derived antileukoproteinase/elafin, constitute a gene family (Lundwall and Lazure, 1995 ;Lundwall, 1996a;Lundwall and Ulvsback, 1996). The genes belonging to this family consist of a characteristic University Hospital, Malmo, S-205 02 Malmo, Sweden three-exon transcription unit in which the nucleotide sequences in the first and the last exon are conserved, whereas the second exon is diss...

Evolution of the Hominoid Semenogelin Genes, the Major Proteins of Ejaculated Semen

“…Dark lines connecting polypeptides represent either noncovalent interactions or transglutaminase cross-linking. The antiparallel orientation and cross-linking involving the Ia and Ib repeats follow those suggested for rodents (Lin et al 2002) and primates (Ulvsback and Lundwall 1997). Stop codons are shown in gorillas as they are in Fig.…”

“…The two semenogelin genes are located on human chromosome 20q, separated by less than 12 kb (Lundwall 1996b). Lundwall (1996b) estimated that the duplication creating the two genes occurred 61 MYA, which is consistent with the observation that at least some New World monkeys possess two semenogelin genes (Ulvsback and Lundwall 1997), although SEMG2 has been truncated by a LINE-1 repeat in the cotton-top tamarin (Lundwall and Olsson 2001).…”

“…In contrast, SEMG2 exhibits no variation in length either between or within species of great apes, but is 180 bp shorter in the gibbon ( Table 2). The SEMG2 gene was reported to be expanded in the rhesus monkey, containing two 3 more 180-bp repeats than humans (Ulvsback and Lundwall 1997). We have found the proboscis monkey (Nasalis larvatus) also to have 10 repeats in SEMG2, and the baboon (Papio sp.)…”

“…Finally, it has recently been shown that both SEMG1 and SEMG2 are expressed at low levels in nonreproductive tissues (Lundwall et al 2002). Robert et al (1997), Ulvsback and Lundwall (1997), and Robert 9 and Gagnon (1999) as described in the text. b Model of molecular interactions involving the SEMG1 protein in the coagulum/plug formation in humans, chimpanzees, and gorillas.…”

The semenogelins: proteins with functions beyond reproduction?

“…Thus, the expressed proteins in this family show wide variation in primary structure. Accordingly, it seems that they have evolved rapidly [11,12], which would explain why semenogelins I and II are apparently found solely in primates, and, even within that taxonomic group, there are obvious interspecies differences in the molecules [13,14]. Rats and mice also express seminal vesicle proteins that belong to the same family and show high sequence similarity in the products encoded by exons one and three, whereas the translated middle exon exhibits little similarity to the primate counterpart [12].…”